1. (

• Archean ,
• Archean_eon ,
• Archean_aeon ,
• Archeozoic ,
• Archaeozoic ,
• Archeozoic_eon ,
• Archaeozoic_aeon

) the time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life ;

1. (

• archean ,
• archaean

) of or relating to the earliest known rocks formed during the Precambrian Eon ;