Source : Webster's Revised Unabridged Dictionary (1913)

Embryonal \Em"bry*o*nal\, a. (Biol.)
   Pertaining to an embryo, or the initial state of any organ;
   embryonic.

Source : WordNet®

embryonal
     adj 1: of or relating to an embryo; "the embryonic membrane" [syn:
            {embryonic}]
     2: of an organism prior to birth or hatching; "in the embryonic
        stage"; "embryologic development" [syn: {embryonic}, {embryologic}]