of, denoting, or formed in the earliest geological era, which lasted for about 4 000 000 000 years before the Cambrian period
noun
2. the Precambrian
Precambrian in American English
(priˈkæmbriən)
adjective
[sometimesp-]
designating or of the division of geologic time covering all the time before the Cambrian Period, equivalent to the Archean Eon and the Proterozoic Eon