Source : Webster's Revised Unabridged Dictionary (1913)

Dehydration \De`hy*dra"tion\, n. (Chem.)
   The act or process of freeing from water; also, the condition
   of a body from which the water has been removed.

Source : WordNet®

dehydration
     n 1: dryness resulting from the removal of water [syn: {desiccation}]
     2: depletion of bodily fluids
     3: the process of extracting moisture [syn: {desiccation}, {drying
        up}, {evaporation}]