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.
feel or handle with the fingers; "finger the binding of the book"
An attachment for a backhoe that allows material to be grasped with the bucket. See example.
The short thick finger situated at an angle to the other fingers so it can be opposed to the them, making it possible to pick up and hold things. The thumb is analogous in position to the big toe (the great toe) and similarly has only two phalanges (all the other digits have three).
In human anatomy, the thumb is the first digit on a hand. The human thumb is fully opposable to the tips of the other fingers in that it may position itself, and be folded inward, toward the rest of the hand and fingers, if so required. It rotates at the carpometacarpal joint and so can complete the sometimes quite delicate task of grasping objects by pressing them against the rest of the hand or finger(s).