Source : Webster's Revised Unabridged Dictionary (1913)

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.