When a male or female takes part in sexual activity within a group of friends but does so in such a way that no one notices because of clever timing and casual body language.
"Where do you think Rob went while he strolled off in the park earlier?"
"He was probably fucking Rosie up that tree"
"Ahhhhh, Smart Casual"
"Why did it take the police so long to track down the rapist?"
"Because he's a Smart Casual rapist, get me?"
When a woman receives a lovely, fully bare bikini wax that appears great at first, but upon closer inspection one finds out -- to their horror -- that the wax has not touched her butt-hole at all...which remains hairy as hell.
I was so excited when my girl told me she got a bikini wax, but as I got up in her business I was horrified to see that her beautifully bare snatch led to a horrible pot of gold that resembled an old man's eyebrows. I realized my girl did not get a full wax at all, she was just going business casual. Bitch.