The Collaborative International Dictionary
co-ed \co-ed\ adj. having both female and male students; -- of a school.
co-ed \co-ed\ n. a female student at a coeducational college or university.
Syn: college girl.
Douglas Harper's Etymology Dictionary
also coed, 1886, American English, (first in Louisa Mae Alcott's "Jo's Boys"); short for "co-educational system;" 1889 as an adjective, short for coeducational; 1893 as a noun meaning "girl or woman student at a co-educational institution."
a. 1 Of an educational institution, that teaches both males and females. 2 Of any location, that mixes males and females. n. 1 (context US dated informal English) A young woman who attends college. 2 (context US dated informal English) A (generally young) woman, especially on the campus of a college or other educational institute.
Usage examples of "co-ed".
The Trampy Co-Ed is the first to die, but only after the mandatory semi-nude swimming scene.
But she was the very image of Chickie, that co-ed girl I'd watched disporting years ago with the Beist-in-the-buckwheat!
Better to have one unreported and unvindicated rape than to rock the very foundations of West Point, to cause doubts about a co-ed academy, to cast suspicion on a thousand innocent men who did not gang-rape a woman that night.