WordNet (r) 3.0 (2006):

Hadean time
    n 1: the earliest eon in the history of the Earth from the first
         accretion of planetary material (around 4,600 million years
         ago) until the date of the oldest known rocks (about 3,800
         million years ago); no evidence of life [syn: Hadean,
         Hadean time, Hadean eon, Hadean aeon, Priscoan,
         Priscoan eon, Priscoan aeon]