The Collaborative International Dictionary of English v.0.48:

Vacuole \Vac"u*ole\, n. [L. vacuus empty: cf. F. vacuole.]
   (Biol.)
   A small air cell, or globular space, in the interior of
   organic cells, either containing air, or a pellucid watery
   liquid, or some special chemical secretions of the cell
   protoplasm.
   [1913 Webster]

   Contractile vacuole. (Zool.) See under Contractile, and
      see Illusts. of Infusoria, and Lobosa.

   Food vacuole. (Zool.) See under Food, and see Illust. of
      Infusoria.
      [1913 Webster]

WordNet (r) 3.0 (2006):

vacuole
    n 1: a tiny cavity filled with fluid in the cytoplasm of a cell

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "vacuole":
   Golgi apparatus, aster, basal body, cell membrane,
   central apparatus, central body, centriole, centroplasm,
   centrosome, centrosphere, chloroplast, chromoplast, cilia,
   cytocentrum, flagella, kinoplasm, microbody, microcentrum,
   mitochondrion, pili, plasmodesmata, plastid, plastosome, ribosome,
   spherosome, spindle fibers