adjective. of or relating to the earliest known rocks formed during the Precambrian Eon.
noun. the time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life.
- Archaeozoic aeon
- Archeozoic eon
- Archean eon
- Archean aeon
- Precambrian period
- Precambrian eon
Example sentences of the word archean
Relatively simple organisms like bacteria and members of the archean domain belong to a category of life called the prokaryotes.