Source : Webster's Revised Unabridged Dictionary (1913)

Flagellum \Fla*gel"lum\, n.; pl. E. {Flagellums}, L. {Flagella}.
   [L., a whip. See {Flagellate}, v. t.]
   1. (Bot.) A young, flexible shoot of a plant; esp., the long
      trailing branch of a vine, or a slender branch in certain
      mosses.

   2. (Zo["o]l.)
      (a) A long, whiplike cilium. See {Flagellata}.
      (b) An appendage of the reproductive apparatus of the
          snail.
      (c) A lashlike appendage of a crustacean, esp. the
          terminal ortion of the antenn[ae] and the epipodite of
          the maxilipeds. See {Maxilliped}.

Source : WordNet®

flagellum
     n 1: a whip used to inflict punishment (often used for pedantic
          humor) [syn: {scourge}]
     2: a lash-like appendage used for locomotion (e.g., in sperm
        cells and some bacteria and protozoa)
     [also: {flagella} (pl)]

flagella
     See {flagellum}