ordovician Meaning, Definition & Usage

  1. noun from 500 million to 425 million years ago; conodonts and ostracods and algae and seaweeds
    Ordovician period.

WordNet

Or`do*vi"cian adjective
Etymology
From L. Ordovices, a Celtic people in Wales.
Definitions
  1. (Geol.) Of or pertaining to a division of the Silurian formation, corresponding in general to the Lower Silurian of most authors, exclusive of the Cambrian. -- n. The Ordovician formation.

Webster 1913