I. |ȯ(r)də|vishən adjective
Usage: usually capitalized
Etymology: Ordovic es, ancient people in northern Wales (from Latin) + English -ian
: of or relating to the period between the Cambrian and the Silurian — called also Lower Silurian ; see geologic time table
II. noun
( -s )
Usage: usually capitalized
: the Ordovician period or system of rocks