Source : Webster's Revised Unabridged Dictionary (1913)

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 : WordNet®

tumbler
     n 1: a gymnast who performs rolls and somersaults and twists etc.
     2: a glass with a flat bottom but no handle or stem; originally
        had a round bottom
     3: a movable obstruction in a lock that must be adjusted to a
        given position (as by a key) before the bolt can be thrown
     4: pigeon that executes backward somersaults in flight or on
        the ground [syn: {roller}, {tumbler pigeon}]