thumb

Etymology

From Middle English thombe, thoume, thoumbe, from Old English þūma, from Proto-West Germanic *þūmō, from Proto-Germanic *þūmô from Proto-Indo-European *tūm- (“to grow”). See also West Frisian tomme, Dutch duim, Low German Duum, German Daumen, Danish tomme, Swedish tumme; also Welsh tyfu (“to grow”), Latin tumēre (“to swell”), Lithuanian tumėti (“to thicken, clot”), Ancient Greek τύμβος (túmbos, “burial mound”), Avestan 𐬀𐬨𐬏𐬙 (amūt, “strong”), Sanskrit तुम्र (túmra, “strong, thick”). The parasitic ‐b has existed since the late 13th century.

noun

1. The short thick digit of the hand that for humans has the most mobility and can be made to oppose (moved to touch) all of the other fingers.
2. (graphical user interface) The part of a slider that may be moved linearly along the slider.
   a scroll-bar thumb
3. (colloquial, Internet) A thumbnail picture.
   2001, Gary, “Wanna See Porn? Take a Look At These (Free Expandable Thumbs) - CLICK HERE”, in alt.sex.services (Usenet):

verb

1. (transitive) To touch or cover with the thumb.
   to thumb the touch-hole of a cannon
   News agencies reported Lavrov had been sent to hospital for a checkup, only for the Russian foreign ministry to rush out a picture of Lavrov in shorts, sporting an Apple watch and Jean-Michel Basquiat-inspired T-shirt, thumbing his notes for his first address at the summit on Tuesday. 2022-11-15, Patrick Wintour, “Sergei Lavrov, a fixture of Russian diplomacy facing his toughest test in Ukraine”, in The Guardian
2. (transitive, with through) To turn the pages of (a book) in order to read it cursorily.
   I thumbed through the book and decided not to bother reading it all.
   It is also disconcerting when you suddenly realise that the driver isn't steering, but may be thumbing over his Customs papers with his feet up. 1948 March and April, “Notes and News: Lines in County Donegal”, in Railway Magazine, page 129
3. (travel) To hitchhike
   So I started thumbin' back east, toward my hometown.
   Bobby thumbed a diesel down, just before it rained. 1969, Kris Kristofferson, Fred Foster, Me and Bobby McGee
   Thumbed a diesel down, outside a cafe. 1980, Kye Fleming, Dennis Morgan, Smoky Mountain Rain
4. To soil or wear with the thumb or the fingers; to soil, or wear out, by frequent handling.
5. To manipulate (an object) with the thumb; especially, to pull back the hammer or open the cylinder of a revolver.
   Fargo palmed out his own revolver, thumbing back the hammer as the barrel came up. 2009, Jon Sharp, The Trailsman #337: Silver Showdown
   Rainford reached down and found the revolver. Thumbing the cylinder open, he inspected the load. 2015, Tony Monchinski, Bad Men (I Kill Monsters Book 3)
   Andy opened the revolver, thumbed in a cartridge. 2015, Don Fitzsimmons, If You Need a Laugh
6. To fire (a single action revolver) quickly by pulling the hammer while keeping the trigger depressed.
   To thumb a single-action revolver, hold down the trigger and use the thumb on the same hand to fire the gun by manipulating the hammer. 2011, Hans-Christian Vortisch, GURPS Tactical Shooting, page 14