The act of engaging in sexual relations with the girlfriend of one of your friends. This can be applied even after they have broken up or if his friend really likes the girl.
"Hey Deuces, you gonna tally one up tonight?"
"Did you see who was all over Bizzle last night? Tally one up for Deuces!"
Person 1: "So what'd you guys do last night?"
Person 2: "I dont know...."
Person 1: "O sit! Tally one up!"