The Collaborative International Dictionary of English v.0.48:

Gymnoplast \Gym"no*plast\ (j[i^]m"n[-o]*pl[a^]st), n. [Gr.
   gymno`s naked + pla`ssein to shape, mold.] (Biol.)
   A cell or mass of protoplasm devoid of an envelope, as a
   white blood corpuscle.
   [1913 Webster]