of, denoting, or formed in the second period of the Palaeozoic era, between the Cambrian and Silurian periods, which lasted for 45 000 000 years during which marine invertebrates flourished
noun
2. the Ordovician
Word origin
C19: from Latin Ordovices ancient Celtic tribe in N Wales
Ordovician in American English
(ˌɔrdəˈvɪʃən)
adjective
[sometimeso-]
designating or of the second geologic period of the Paleozoic Era, characterized by the development of abundant marine invertebrates and the first vertebrates