neck with (one)
old-fashioned slang To kiss and caress one passionately and for an extended period of time. The cars parked in "Lover's Lane" are filled with high school students necking with their boyfriends and girlfriends. If you hadn't been so busy necking with that guy, you might have realized we were all leaving the club!
neck with someone
to engage in amorous kissing and caressing with someone. Ted is over there necking with Molly. Molly is necking with Ted and thinking of Ken.