Source : Webster's Revised Unabridged Dictionary (1913)

Vesicle \Ves"i*cle\, n. [L. vesicula, dim. of vesica a bladder,
   blister; akin to Skr. vasti bladder: cf. F. v['e]sicule.]
   A bladderlike vessel; a membranous cavity; a cyst; a cell.
   Specifically:
   (a) (Bot.) A small bladderlike body in the substance of
       vegetable, or upon the surface of a leaf.
   (b) (Med.) A small, and more or less circular, elevation of
       the cuticle, containing a clear watery fluid.
   (c) (Anat.) A cavity or sac, especially one filled with
       fluid; as, the umbilical vesicle.
   (d) (Zo["o]l.) A small convex hollow prominence on the
       surface of a shell or a coral.
   (e) (Geol.) A small cavity, nearly spherical in form, and
       usually of the size of a pea or smaller, such as are
       common in some volcanic rocks. They are produced by the
       liberation of watery vapor in the molten mass.

Source : WordNet®

vesicle
     n : a small anatomically normal sac or bladderlike structure
         (especially one containing fluid) [syn: {cyst}]