Definition of plesiomorphy in US English:

plesiomorphy

noun

Taxonomy
  • The state of being plesiomorphic; ancestral or primitive condition as compared to a later, derived character state. Also (as a count noun): an ancestral or plesiomorphic feature or trait.

Origin

1960s; earliest use found in Systematic Zoology. From plesio- + -morphy, after plesiomorphic, plesiomorphous.

Pronunciation

plesiomorphy

/ˈpliːzɪəmɔːfi/