hyperadult

adjective2

1. •
   Having excessively or inappropriately adult characteristics.

   • As matters now stand, "programs" too often result in the formation of individuals whose intelligence may be hyperadult, but whose affective and moral sensibility is childish. — 1966
2. •
   Exhibiting hypermorphosis; Having features that exaggerate adult morphology.

   • This suggests a heterochronic event, such as a hypermorphosis (i.e., hyperadult size and shape, McNamara, 1986). — 2003