Webster's Revised Unabridged Dictionary · 1913

Thumb

Thumb , noun

[Old English thombe, thoumbe, þume, Anglo-Saxon þūma; akin to OFries. thūma, Dutch duim, German daumen, Old High German dūmo, Icelandic þumall, Danish tommelfinger, Swedish tumme, and perhaps to Latin tumere to swell. r56. Compare Thimble, Tumid.]

The short, thick first digit of the human hand, differing from the other fingers in having but two phalanges; the pollex. See Pollex.
Upon his thumb he had of gold a ring. — Chaucer
Collocations (8)
Thumb band , a twist of anything as thick as the thumb. — Mortimer
Thumb blue , indigo in the form of small balls or lumps, used by washerwomen to blue linen, and the like.
Thumb latch , a door latch having a lever formed to be pressed by the thumb.
Thumb mark , (a) The mark left by the impression of a thumb, as on the leaves of a book. — Longfellow (b) The dark spot over each foot in finely bred black and tan terriers.
Thumb nut , a nut for a screw, having wings to grasp between the thumb and fingers in turning it; also, a nut with a knurled rim for the same perpose.
Thumb ring , a ring worn on the thumb. — Shakespeare
Thumb stall (Military) , (a) A kind of thimble or ferrule of iron, or leather, for protecting the thumb in making sails, and in other work. A buckskin cushion worn on the thumb, and used to close the vent of a cannon while it is sponged, or loaded.
Under one's thumb , completely under one's power or influence; in a condition of subservience. [Colloquial]

Thumb , transitive verb

1.
To handle awkwardly. — Johnson
2.
To play with the thumbs, or with the thumbs and fingers; as, to thumb over a tune.
3.
To soil or wear with the thumb or the fingers; to soil, or wear out, by frequent handling; also, to cover with the thumb; as, to thumb the touch-hole of a cannon.
He gravely informed the enemy that all his cards had been thumbed to pieces, and begged them to let him have a few more packs. — Macaulay

Thumb , intransitive verb

To play with the thumb or thumbs; to play clumsily; to thrum.