Used attributively in noun phrases such as "girlfriend jeans"; treated as an adjective in the dictionary.
Definitions
girlfriendnoun
A female partner in a romantic relationship.
He introduced his girlfriend to his family at the dinner party.
A female friend.
She went shopping with her girlfriend on Saturday.
girlfriendadjective
Designating or characteristic of something intended for or associated with a girlfriend; styled in a way perceived as casual or borrowed from a romantic partner.
She prefers the relaxed fit of girlfriend jeans for everyday wear.