The Collaborative International Dictionary of English v.0.48:

Bass drum \Bass` drum"\ (Mus.)
   The largest of the different kinds of drums, having two
   heads, and emitting a deep, grave sound. See Bass, a.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Drum \Drum\, n. [Cf. D. trom, trommel, LG. trumme, G. trommel,
   Dan. tromme, Sw. trumma, OHG. trumba a trumpet, Icel. pruma a
   clap of thunder, and as a verb, to thunder, Dan. drum a
   booming sound, drumme to boom; prob. partly at least of
   imitative origin; perh. akin to E. trum, or trumpet.]
   1. (Mus.) An instrument of percussion, consisting either of a
      hollow cylinder, over each end of which is stretched a
      piece of skin or vellum, to be beaten with a stick; or of
      a metallic hemisphere (kettledrum) with a single piece of
      skin to be so beaten; the common instrument for marking
      time in martial music; one of the pair of tympani in an
      orchestra, or cavalry band.
      [1913 Webster]

            The drums cry bud-a-dub.              --Gascoigne.
      [1913 Webster]

   2. Anything resembling a drum in form; as:
      (a) A sheet iron radiator, often in the shape of a drum,
          for warming an apartment by means of heat received
          from a stovepipe, or a cylindrical receiver for steam,
          etc.
      (b) A small cylindrical box in which figs, etc., are
          packed.
      (c) (Anat.) The tympanum of the ear; -- often, but
          incorrectly, applied to the tympanic membrane.
      (d) (Arch.) One of the cylindrical, or nearly cylindrical,
          blocks, of which the shaft of a column is composed;
          also, a vertical wall, whether circular or polygonal
          in plan, carrying a cupola or dome.
      (e) (Mach.) A cylinder on a revolving shaft, generally for
          the purpose of driving several pulleys, by means of
          belts or straps passing around its periphery; also,
          the barrel of a hoisting machine, on which the rope or
          chain is wound.
          [1913 Webster]

   3. (Zool.) See Drumfish.
      [1913 Webster]

   4. A noisy, tumultuous assembly of fashionable people at a
      private house; a rout. [Archaic]
      [1913 Webster]

            Not unaptly styled a drum, from the noise and
            emptiness of the entertainment.       --Smollett.
      [1913 Webster]

   Note: There were also drum major, rout, tempest, and
         hurricane, differing only in degrees of multitude and
         uproar, as the significant name of each declares.
         [1913 Webster]

   5. A tea party; a kettledrum. --G. Eliot.
      [1913 Webster]

   Bass drum. See in the Vocabulary.

   Double drum. See under Double.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bass drum
    n 1: a large drum with two heads; makes a sound of indefinite
         but very low pitch [syn: bass drum, gran casa]