slang To kiss passionately and with an open mouth; to French kiss. I went to see a movie with Tom and Janet, but they spent the whole time swapping spits! A: "Did you get lucky on your date last night, dude?" B: "We swapped spit for a while, but that's about it."
See also: swap
tv. to kiss with someone. Tiffany and Wilbur were off somewhere swapping spits, I guess.