go out with
go (out) with (someone)
To date someone. A: "I hear that Kevin is going out with Katie—is that true?" B: "Yeah, they're a couple now." I'm going with Brad, so you better stop flirting with him!
See also: go
go out with something
to go out of fashion at the same time as something else went out of fashion. That style of dress went out with the bustle. Your thinking went out with the horse and buggy.