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)
Idiom of the Day
put out (some) feelers or put (some) feelers out
to attempt to find out something without being too obvious about it
I put out some feelers to see if it would be easy to find another job.