Source : Webster's Revised Unabridged Dictionary (1913)

Bumblebee \Bum"ble*bee`\, n. [OE. bumblen to make a humming
   noise (dim. of bum, v. i.) + bee. Cf. {Humblebee}.]
   (Zo["o]l.)
   A large bee of the genus {Bombus}, sometimes called
   {humblebee}; -- so named from its sound.

   Note: There are many species. All gather honey, and store it
         in the empty cocoons after the young have come out.

Source : WordNet®

bumblebee
     n : robust hairy social bee of temperate regions [syn: {humblebee}]