When a man is having sex on top of a woman, he spreads his leg and arms out and “leap-frogs” his cock into her mouth. This is performed to minimize the "air-time" from vagina (or anus) to mouth when the man is about to cum.
Simon: "I tried to cum in Mrs. Robinson's mouth, but couldn't make it in time. I blew it all over her tits."
Garfunkel: "Dude. You should've given her the ole' sexy frog. It great for just launching into place. Turn up."
Sexy Frog def: The meaning of witch sex with a frog in a tux