paedomorphism

n.
  1. Retention of juvenile characteristics in the adult, occurring in mammals.
  2. Description of adult behavior in terms appropriate to child behavior.
Related formspae′do•morphic (-fĭk) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.