The Collaborative International Dictionary
Impuberal
Impuberal \Im*pu"ber*al\ ([i^]m*p[=u]"b[~e]r*al), a. Not having arrived at puberty; immature.
In impuberal animals the cerebellum is, in proportion
to the brain proper, greatly less than in adults.
--Sir
W. Hamilton.
Wiktionary
impuberal
a. (context rare English) immature; not having come to puberty.