Definition of pachycephalic in English:

pachycephalic

Pronunciation /ˌpakɪsɪˈfalɪk/ /ˌpakɪkɪˈfalɪk/

adjective

rare Anthropology
  • Having a very thick skull; exhibiting pachycephaly. Later also (humorous): thickheaded, stupid.

Origin

Late 19th century; earliest use found in Journal of the Royal Anthropological Institute. From pachy- + -cephalic, after scientific Latin Pachycephali thick heads.