A way of describing an
ambiguous relationship between a man (or woman) and another woman. The individuals have sex, and have a close personal relationship, but the woman
in question is
not defined by her lover as a girlfriend, so she can only be referred to as a 'girl thing'.
person 1: what's up with chris and laura,
they live and sleep together, are they going out?
person 2: no, she's just his girl thing.
Are they
friends with benefits? Are they in an
open relationship? We don't know, so we'll call her a girl thing.