Synonyms for Full-grown:

adj.

adult (adjective)
serious, adult, virile, of age, reasonable, nubile, developed, grown up, mature.
developed (adjective)
mature, ripe.
entire (adjective)
sum, full-fledged, gross, all-embracing, sweeping, all, full-scale, global, comprehensive, total, tally, whole, exhaustive, mass, holistic, full, conclusive, entire, all-inclusive, complete.

n.

grown up, ripe, full-blown, youth. full-grown (noun)
fully grown, mature, big, grownup, grown, adult.

Other synonyms:

full-blown, fully fledged. infantile, grown up. ripe. growth. Other relevant words:
ripe, grown up, full-blown, fully fledged, big, grown, grownup, fully grown.