The Collaborative International Dictionary of English v.0.48:

Gymnospermous \Gym`no*sper"mous\ (j[i^]m"n[-o]*sp[~e]r"m[u^]s),
   a. [Gr. gymno`spermos; gymno`s naked + spe`rma seed: cf. F.
   gymnosperme.] (Bot.)
   (a) Having naked seeds, or seeds not inclosed in a capsule or
       other vessel.
   (b) Belonging to the class of plants consisting of
       gymnosperms.
       [1913 Webster]

WordNet (r) 3.0 (2006):

gymnospermous
    adj 1: relating to or characteristic of plants of the class
           Gymnospermae