The Collaborative International Dictionary of English v.0.48:

Anhydrous \An*hy"drous\, a. [Gr. ? wanting water; 'an priv. +
   "y`dwr water.]
   Destitute of water; as, anhydrous salts or acids.
   [1913 Webster] Ani

WordNet (r) 3.0 (2006):

anhydrous
    adj 1: without water; especially without water of
           crystallization [ant: hydrated, hydrous]

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "anhydrous":
   Saharan, arid, athirst, bone-dry, desert, droughty, dry,
   dry as dust, dusty, high and dry, juiceless, like parchment, sandy,
   sapless, thirsting, thirsty, undamped, unwatered, waterless