The Collaborative International Dictionary of English v.0.48:

Inspissate \In*spis"sate\, v. t. [imp. & p. p. Inspissated; p.
   pr. & vb. n. Inspissating.] [L. inspissatus, p. p. of
   inspissare to thicken; pref. in- + spissare to thicken, fr.
   spissus thick.]
   To thicken or bring to greater consistence, as fluids by
   evaporation.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Inspissate \In*spis"sate\, a. [L. inspissatus, p. p.]
   Thick or thickened; inspissated. --Greenhill.
   [1913 Webster]

WordNet (r) 3.0 (2006):

inspissate
    v 1: make viscous or dense; "thicken the sauce by adding flour"
         [syn: thicken, inspissate]
    2: make thick or thicker; "Thicken the sauce"; "inspissate the
       tar so that it becomes pitch" [syn: thicken, inspissate]
       [ant: thin]
    3: become thick or thicker; "The sauce thickened"; "The egg yolk
       will inspissate" [syn: thicken, inspissate] [ant: thin]