Tumbler \Tum"bler\, n.

1. One who tumbles; one who plays tricks by various motions of the body; an acrobat.

2. A movable obstruction in a lock, consisting of a lever, latch, wheel, slide, or the like, which must be adjusted to a particular position by a key or other means before the bolt can be thrown in locking or unlocking.

3. (Firearms) A piece attached to, or forming part of, the hammer of a gunlock, upon which the mainspring acts and in which are the notches for sear point to enter.

4. A drinking glass, without a foot or stem; -- so called because originally it had a pointed or convex base, and could not be set down with any liquor in it, thus compelling the drinker to finish his measure.

5. (Zo["o]l.) A variety of the domestic pigeon remarkable for its habit of tumbling, or turning somersaults, during its flight.

6. (Zo["o]l.) A breed of dogs that tumble when pursuing game. They were formerly used in hunting rabbits.

7. A kind of cart; a tumbrel. [Prov. Eng. & Scot.]

Source: Webster's Revised Unabridged Dictionary (1913)