This is from an episode of the series "Family guy". There's a group of 4 friends in a bar, one of them is called Jerome, he is black and he talks with an African-American vernacular accent. He says: "Hey, you know what they say. See a broad, to get that booty, yak 'em. Leg her down and smack 'em yak 'em!" I've searched the meaning on the net, and I found some references to a movie in the 80s, and I believe that the phrase has some sexual meaning, but I'd like to know what it exactly means.