ply

Etymology 1

From Middle English pleit, plit, plite (“a fold, pleat, wrinkle; braid, strand in a braided cord, ply”), from Anglo-Norman pli, plei, pleit, and Middle French pli, ploy, ply (“a fold, pleat; joint in armour; situation, state”) (modern French pli (“a fold, pleat”)), from plier, ployer (“to bend, fold”), from Latin plicāre, present active infinitive of plicō (“to bend, fold, roll up”), from Proto-Indo-European *pleḱ- (“to fold, plait, weave”).

noun

1. A layer of material.
   two-ply toilet paper
   It is possible to have a very well load balanced partition but with such a high ply that its slowest piece is slower than a not-so-well balanced partition with less ply. 1999, Twelfth International Conference on VLSI Design: Proceedings: January 7–10, 1999, Goa, India, Los Alamitos, Calif.: IEEE Computer Society Press, page 313
   The designer critic's staff would come in with, for example, loads of three-ply cashmere. The students weren't even selecting their own fabrics. 2015 October, Tim Gunn, with Ada Calhoun, “Repositioning the Parsons Fashion Design Program”, in Tim Gunn: The Natty Professor: A Master Class on Mentoring, Motivating, and Making it Work!, trade paperback edition, New York, N.Y.: Gallery Books, part I (Truth Telling), page 49
2. A strand that, twisted together with other strands, makes up rope or yarn.
   To make the hail rod a rope of straw is the first thing necessary; it must be made of ripe wheat straw, soaked and twisted, plaited with three strand and then with four ply, making twelve strand to the rope. 1837 August, “Art I. Protection against Hail Storms. Notice and Description of the Paragrèle, or Hail Rod. By A. J. Downing, Botanic Garden and Nurseries, Newbergh, N.Y.”, in C. M. Hovey, editor, The Magazine of Horticulture, Botany, and All Useful Discoveries and Improvements in Rural Affairs, volume III, number VIII (number XXXII overall), Boston, Mass.: Published by Hovey & Co.,[…]; New York, N.Y.: Israel Post,[…], →OCLC, page 281
3. (colloquial) Short for plywood.
   The Standards describe the quality of timber or ply, moisture content, amount of acceptable sapwood, freedom from decay and insect attack, limitation of checks and splits and treatment of resin staining, and the way plugging may be employed to mask defects in ply faces. 1994, Alan Blanc, “Doors”, in Mitchell’s Internal Components (Mitchell’s Building Series), Essex: Longman Scientific & Technical; republished London: Routledge, 2014, section 6.5 (Flush Doors)
   Teak-faced ply is about three times the price of any other, so if you need to economise, anything other than teak would be a good choice! Similarly, marine ply is substantially more expensive than exterior ply, so it may be preferable to go with the latter option. 2015, “Hull and Deck”, in Judith Chamberlain-Webber, editor, The Boat Improvement Bible: Practical Projects to Customise and Upgrade Your Boat, London: Adlard Coles Nautical, page 39, column 1
4. (artificial intelligence, combinatorial game theory) In two-player sequential games, a "half-turn" or a move made by one of the players.
   He proposed to build Deep Purple, a super-computer capable of 24-ply look-ahead for chess.
   Chinook uses an iterative, alpha-beta search with transposition tables and the history heuristic[…]. Under tournament conditions (thirty moves an hour), the program searches to an average minimum depth of nineteen ply (one ply is one move by one player). The search uses selective deepening to extend lines that are tactically or positionally interesting. Consequently, major lines of play are often searched many plies deeper. It is not uncommon for the program to produce analyses that are thirty-ply deep or more. 1996, Jonathan Schaeffer, Robert Lake, “Solving the Game of Checkers”, in Richard J. Nowakowski, editor, Games of No Chance: Combinatorial Games at MSRI, 1994 (Mathematical Sciences Research Institute Publications; 29), Cambridge: Cambridge University Press, page 122
   Two principal search strategies were (correctly) predicted: Type-A programs that apply "brute force" inspection of every possible position over a fixed number of plys; and Type-B programs that prune potential moves according to some selection function and then examine the significant sets over as many plys as practical and only at those positions reflecting a degree of stability. 2009, Richard A. Epstein, “Games of Pure Skill and Competitive Computers”, in The Theory of Gambling and Statistical Logic, 2nd edition, Burlington, Mass.: Academic Press; special edition, Waltham, Mass., Kidlington, Oxfordshire: Academic Press, 2013, page 380
5. (now chiefly Scotland) A condition, a state.

Etymology 2

From Middle English plīen, pli, plie (“to bend, fold, mould, shape; to be flexible; to be submissive, humble oneself; to compel someone to submit”), from Anglo-Norman plier, plaier, pleier, ploier, and Middle French plier, ployer (“to bend, fold; to be submissive; to compel someone to submit”) (modern French plier, ployer), from Old French ploiier, pleier (“to fold”), from Latin plicāre (“to fold”); see further at etymology 1. The word is cognate with Catalan plegar (“to bend, fold”), Italian piegare (“to bend, fold, fold up”), Old Occitan plegar, plejar, pleyar (“to fold”) (modern Occitan plegar), Spanish plegar (“to fold”).

verb

1. (transitive, obsolete) To bend; to fold; to mould; (figurative) to adapt, to modify; to change (a person's) mind, to cause (a person) to submit.
   And now when at length the Vineyard has ſhed its late Leaves, and the cold Northwind ſhook from the Groves their Honours; even then the active Swain extends his Cares to the enſuing Year, and cloſe plys the deſolate forſaken Vine, cutting off the ſuperfluous Roots with Saturn's crooked Hook, and forms it by pruning. 1743, Virgil, “The Georgics of Virgil. Book II.”, in [Joseph Davidson], transl., The Works of Virgil Translated into English Prose, […] In Two Volumes, volume I, London: Printed for Joseph Davidson,[…], →OCLC, page 135
2. (intransitive) To bend, to flex; to be bent by something, to give way or yield (to a force, etc.).

Etymology 3

From apply; compare Middle English plīen, pli, plie, pleie (“to place (something) around, on, or over, to cover; to apply, use; to strive”), short for aplīen, applīen (“to combine, join; to attach; to assemble; to use, be of use; to allot; to apply; to inflict; to go; to ply, steer; to comply, submit”), from Old French applier, aplier, aploier (“to bend; to apply”), from Latin applicāre, present active infinitive of applicō (“to apply; to attach, join; to add”), from ad- (“prefix meaning ‘to, towards’”) + plicō (“to bend, fold, roll up”); see further at etymology 1.

verb

1. (transitive) To work at (something) diligently.
   He plied his trade as carpenter for forty-three years.
   Ply you your work or elſe you are like to ſmart. 1595, G[eorge] P[eele], The Old Wiues Tale.[…], printed at London: By Iohn Danter, and are to be sold by Raph Hancocke, and Iohn Hardie, →OCLC; reprinted as The Old Wives Tale, 1595 (The Malone Society Reprints; 7), Oxford: Printed for the Malone Society by Horace Hart M.A., at the Oxford University Press, 1908 (February 1909 reprint), →OCLC, line 720
   But English Courage growing as they fight, / In danger, noise, and slaughter takes delight, / Their bloody Task, unwearied, still they ply, / Only restrain’d by Death, or Victory: […] 1666, Edm[und] Waller, Instructions to a Painter, for the Drawing of the Posture & Progress of His Ma[jes]ᵗⁱᵉˢ Forces at Sea, under the Command of His Highness Royal.[…], London: Printed for Henry Herringman,[…], →OCLC, page 13
2. (transitive) To wield or use (a tool, a weapon, etc.) steadily or vigorously.
   He plied his ax with bloody results.
   He [a carpenter] feels an additional particle of new life coursing through his veins, and he plys the plane on the following day with additional energy to his own and to his master's satisfaction. 1854, “St. Valentine’s Day”, in The Favorite, volume I, London: Partridge, Oakey, and Co.[…], →OCLC, page 114
   Drink had dispelled all common prudence, and chuckling at the idea of finding treasures unknown to their comrades, they plied the crowbar to the door, which was locked, but it soon yielded. 1863, [James Pascoe], “Death in the Vaults”, in The Brigantine. A Story of the Sea. In Two Volumes, volume I, London: Richard Bentley,[…], →OCLC, page 299
   [T]his abuse is as outrageous as are the acts of any Ku-Klux that ever plied the lash or sounded a whistle, […] 24 February 1871, B. F. Sawyer, “The Ku-Klux—The Atlanta Sun and Bullock’s Proclamation”, in Rome Courier; quoted in Testimony Taken by the Joint Select Committee to Inquire into the Condition of Affairs in the Late Insurrectionary States. Georgia, volume II, Washington, D.C.: Government Printing Office, 1 November 1871, published 1872, →OCLC, page 883
3. (transitive) To press upon; to urge persistently.
   to ply someone with questions or solicitations
4. (transitive) To persist in offering something to, especially for the purpose of inducement or persuasion.
   to ply someone with drink
   Esther began […] to cry. But when the fire had been lit specially to warm her chilled limbs and Adela had plied her with hot negus she began to feel rather a heroine. 1929, M. Barnard Eldershaw [pseudonym; Marjorie Barnard and Flora Eldershaw], chapter VII, in A House is Built, London: George G. Harrap and Co., →OCLC, section VI
5. (transitive, intransitive, transport) To travel over (a route) regularly.
   to ply the seven seas
   The steamer plies between several ports on the coast.
   [T]he ſaid corporation ſhall and may be authorized and required to licenſe all ſuch perſon or perſons as ſhall keep or drive any cars, drays or carts, plying for hire within the ſaid town of Wexford, 1794, “Chap. XXVI. An Act for the Improvement of the Town and Harbour of Wexford, and for Building a Bridge or Bridges over the River Slaney, at or near said Town.”, in Statutes Passed in the Parliaments Held in Ireland, volume X, Dublin: Printed by George Grierson,[…], published 1799, →OCLC, section LXXIII, page 56
   An act of parliament, empowering the plaintiffs, a company, to ply on Sundays from certain points on the south bank of the Thames, but imposing no obligation to provide means of transport or to maintain their plying-places, does not confer an exclusive right against the rest of the world, such as the Court of Chancery will interfere to protect; […] 21 March 1866, “Letton v. Goodden”, in Montagu Chambers, Francis Towers Streeten, Frederick Hoare Colt, editors, The Law Journal Reports for the Year 1866:[…], volumes XXXV (New Series; volume XLIV overall), part I (Chancery and Bankruptcy), London: Printed by James Holmes,[…]; [p]ublished by Edward Bret Ince,[…], →OCLC, headnote, page 427, column 1
   Steam navigation is in its infancy: four small 600-ton steamers ply between Hankow, Changsha, and Siangtan; and there are also perhaps a score of launches plying in and out of the province. 1907, Mark Tennien, edited by Marshall Broomhall, The Chinese Empire: A General & Missionary Survey, London: Morgan & Scott, page 169
   Before the bridging of the Forth, the train ferry which plied across the estuary from Granton to Burntisland was inconvenient, slow, and uncomfortable, and although an alternative route was available, it meant a detour by rail of 70 miles via Stirling …. 1941 January, the late John Phillimore, “The Forth Bridge 1890-1940”, in Railway Magazine, page 5
6. (intransitive, obsolete) To work diligently.
7. (intransitive, nautical, obsolete) To manoeuvre a sailing vessel so that the direction of the wind changes from one side of the vessel to the other; to work to windward, to beat, to tack.
   Weighed anchor about five morn, and plied till about noon, and then anchored. This day, at morn, went about the general to council: the result was, the fleet should ply near, as with convenience, to the Texel, to prevent a conjunction of those ships there with Admiral [Maarten] Tromp; […] 21 July 1653, William Penn, Granville Penn, “A Journal on the Vanguard”, in Memorial of the Professional Life and Times of Sir William Penn, Knt. Admiral and General of the Fleet, during the Interregnum; Admiral and Commissioner of the Admiralty and Navy, after the Restoration. From 1644 to 1670. … In Two Volumes, volume I, London: James Duncan,[…], published 1833, →OCLC, page 535

noun

1. A bent; a direction.