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
throw the book at (someone)
to punish someone severely for breaking a rule or the law
The judge threw the book at the man after he was convicted of robbing a bank.