At the end of sex when the man is ready to finish, he stands behind the girls' head and rests his penis on the top and busts the load forward. The penis is the unicorn horn. GET IT!?
"Yeah Jamal, I was with Shanicequa yesterday. We decided to get it on you know, and I finished with the unicorn. She got pretty pissed because I fucked up the upholstery on her new love seat. The Unicorn Finish was pretty fun though. know what I'm sayin'?"