Definition of plesiomorphic in English:

plesiomorphic

Pronunciation /ˌpliːzɪəˈmɔːfɪk/

adjective

  • Of a trait or characteristic: primitive and ancestral; specifically present in organisms outside a clade or group under consideration, and so not distinctively characteristic of members of that clade or group (and presumed to derive from a more distant common ancestor). Compare plesiomorphous . Opposed to apomorphic.

Origin

Mid 19th century (in an earlier sense). From plesio- + -morphic.