variants:
or chiefly British aeon
Definition of eon
1
: an immeasurably or indefinitely long period of time : age
I haven't seen him in eons.
2a
: a very large division of geologic time usually longer than an era
the Archean eon
b
: a unit of geologic time equal to one billion years
Test Your Vocabulary
Commonly Confused Words Quiz
-
- I went to the ______ store to buy a birthday card.

Test your vocabulary with our 10-question quiz!
TAKE THE QUIZ
A daily challenge for crossword fanatics.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Share eon
Time Traveler for eon
The first known use of eon was circa 1642
See more words from the same year