thumb

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The short thick digit of the human hand, next to the index finger and opposable to each of the other four digits.
• noun A corresponding digit in other animals, especially primates.
• noun The part of a glove or mitten that covers the thumb.
• noun Architecture An ovolo.
• intransitive verb To scan (written matter) by turning over pages with or as if with the thumb.
• intransitive verb To disarrange, soil, or wear by careless or frequent handling.
• intransitive verb Informal To solicit (a ride) from a passing vehicle by signaling with the thumb.
• intransitive verb To scan written matter by turning over pages with or as if with the thumb.
• intransitive verb Informal To hitchhike.
• idiom (all thumbs) Lacking physical coordination, skill, or grace; clumsy.
• idiom (thumb (one's) nose) To express scorn or ridicule, often by placing the thumb on the nose and wiggling the fingers.
• idiom (under (someone's) thumb) Under the control of someone; subordinate to.

from The Century Dictionary.

• To handle or perform awkwardly: as, to thumb over a tune.
• To soil or wear out with much handling; hence, to use, read, or turn over the pages of (as a book).
• To turn (one's glass) over the thumb: an old custom when persons were drinking together, intending to show that the glass had been emptied so that the small drop remaining would lie on the thumb-nail without running off. Compare supernaculum.
• To cover with the thumb, as the vent of a muzzle-loading cannon.
• noun In geology, a columnar projection of eruptive rock.
• noun The shortest and thickest finger of the human hand; the pollex; the first digit of the hand, on the radial side, next to the index or forefinger.
• noun The inner, radial, or first digit of the fore paw of any animal. When there are five digits, the first of these always corresponds to the human thumb; otherwise not.
• noun The movable radial digit of a bird's manus or pinion, which bears the packet of feathers called the alula or bastard wing, and which is usually movable apart from the rest of the bones.
• noun The thumb of the foot; the hallux; the inner digit of the foot, called the great toe in man.
• noun The hind toe of a bird (except a three-toed woodpecker); the hallux; when there are two hind toes, the inner one of these (except in trogons).
• noun Palpitation of the heart in domestic animals, as the horse, the result of functional or organic disease. See palpitation.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb To play with the thumb or thumbs; to play clumsily; to thrum.
• transitive verb To handle awkwardly.
• transitive verb To play with the thumbs, or with the thumbs and fingers.
• transitive verb To soil or wear with the thumb or the fingers; to soil, or wear out, by frequent handling; also, to cover with the thumb.
• noun The short, thick first digit of the human hand, differing from the other fingers in having but two phalanges; the pollex. See pollex.
• noun a twist of anything as thick as the thumb.
• noun indigo in the form of small balls or lumps, used by washerwomen to blue linen, and the like.
• noun a door latch having a lever formed to be pressed by the thumb.
• noun The dark spot over each foot in finely bred black and tan terriers.
• noun 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.
• noun a ring worn on the thumb.
• noun (Mil.) A buckskin cushion worn on the thumb, and used to close the vent of a cannon while it is sponged, or loaded.
• noun [Colloq.] completely under one's power or influence; in a condition of subservience.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun 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.
• noun computing The part of a slider that may be moved linearly along the slider.
• noun colloquial, Internet A thumbnail picture.
• verb transitive To touch with the thumb.
• verb transitive To turn the pages of (a book) in order to read it cursorily.
• verb travel To hitchhike

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb feel or handle with the fingers
• noun the part of a glove that provides a covering for the thumb
• noun a convex molding having a cross section in the form of a quarter of a circle or of an ellipse
• verb travel by getting free rides from motorists
• noun the thick short innermost digit of the forelimb
• verb look through a book or other written material