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]

The Collaborative International Dictionary of English v.0.48:

lyophilize \lyophilize\ v. t.
   to freeze-dry; -- a technique used to dry serum, tissue,
   unstable chemicals and other sensitive materials.
   [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

lyophilize
    v 1: to dry (blood, serum, or tissue) by freezing in a high
         vacuum [syn: lyophilize, lyophilise]