plumb

Etymology 1

From Middle English plumbe, plumme, from Old French *plombe, from Latin plumba, plural of plumbum.

adj

1. Truly vertical, as indicated by a plumb line.
2. (cricket) Describing an LBW where the batsman is hit on the pads directly in front of their wicket and should be given out.

adv

1. In a vertical direction; perpendicularly.
2. (informal) Squarely, directly; deeply, completely.
   It hit him plumb in the middle of his face.
   Years ago the well plumb dried out, not a drop of water in there since.
   'Are you sure of that, M. Hardman?' 'I'm plumb certain.'. 1934, Agatha Christie, chapter 9, in Murder on the Orient Express, London: HarperCollins, published 2017, page 143

noun

1. A little mass of lead, or the like, attached to a line, and used by builders, etc., to indicate a vertical direction.
2. (nautical) A weight on the end of a long line, used by sailors to determine the depth of water.
3. The perpendicular direction or position.

verb

1. To determine the depth, generally of a liquid; to sound.
2. To attach to a water supply and drain.
3. (transitive, figurative) To think about or explore in depth, to get to the bottom of, especially to plumb the depths of.
   Delving to the core of her heart, his blue-green eyes plumbed her psyche, stripping it of all defenses, all resolve. 2011, Catherine Lanigan, The Texan
   The pressure had been on City, on Guardiola, to deliver the trophy that Sheikh Mansour has craved since his takeover in 2008 but it was an occasion when the manager found a new way to lose, to plumb fresh depths of frustration. May 29 2021, David Hytner, “Chelsea win Champions League after Kai Havertz stuns Manchester City”, in The Guardian
4. To use a plumb bob as a measuring or aligning tool.
5. To accurately align vertically or horizontally.
6. (dated) To seal something with lead.
7. (intransitive) To work as a plumber.
8. (rare) To fall or sink like a plummet.
9. (US, colloquial, figurative, obsolete) To trace a road or track; to follow it to its end.
10. (nautical) To position vertically above or below.

Etymology 2

noun

1. Obsolete form of plum (“the fruit”).
   Without attending to sub-divisions, all the pears are of one species, as well as all the apples, plumbs, peaches, cherries, lemons, citrons, oranges […] 1767, Select Essays on Husbandry