Source : WordNet®

Priscoan aeon
     n : 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}]