Adjective: having the same age or date of origin; contemporary.
Noun: a person of roughly the same age as oneself; a contemporary.
Origin: Latin coaevus, from co- ‘in common’ + aevum ‘age’.
TO pile like Thunder to its close,
Then crumble grand away,
While everything created hid—
This would be Poetry:
Or Love,—the two coeval came—
We both and neither prove,
Experience either, and consume—
For none see God and live.
Emily Dickinson, Part Five: The Single Hound - CXLII, Complete Poems. 1924.
The old people appeared remarkably well preserved, as if by the saltness of the atmosphere, and after having once mistaken, we could never be certain whether we were talking to a coeval of our grandparents, or to one of our own age.
Henry David Thoreau, Cape Cod (1855-1865), in The Writings of Henry David Thoreau, vol. 4, pp. 257-258, Houghton Mifflin (1906)