The Collaborative International Dictionary of English v.0.48:

Freeze-dry \Freeze"-dry`\ (fr[=e]z"-dr[imac]`), v. t. [imp. & p.
   p. Freeze-dried; p. pr. & vb. n. Freeze-drying.]
   to remove the moisture from (e.g. food) by first freezing and
   then subjecting to a high vacuum; -- used as a mild method
   for drying foods or chemicals while causing little
   decomposition, in contrast to heat-drying.

   Note: This is a relatively gently drying process used to
         preserve food or sensitive biological materials. For
         biochemical materials, the term lyophilize is often
         used.
         [PJC]

WordNet (r) 3.0 (2006):

freeze-drying
    n 1: a method of drying food or blood plasma or pharmaceuticals
         or tissue without destroying their physical structure;
         material is frozen and then warmed in a vacuum so that the
         ice sublimes [syn: freeze-drying, lyophilization,
         lyophilisation]