I was watching the film The Perks of Being a Wallflower. The context was a girl and a boy were talking about their mutual friend Bod. The girl said that Bob is still trying to shag that waitress from the Olive Garden. And then the boy replied: he is never tossing the salad.
So what does it mean?
If you are actually talking about a lettuce salad, "toss the salad" is simply what you do to distribute the dressing evenly among the lettuce leaves. It's used that way all the time. I had never come across the vulgar meaning before, but I suppose that someone thought it would be funny to refer to having sex with the waitress as 'tossing a salad" because the Olive Garden is a restaurant known for its salads.
It's a very vulgar euphemism, look it up at Urban Dictionary if you dare...
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It's disgusting. Does it really mean that way? I mean when someone use the phrase, can it just mean sexual intercourse?
It's also used when you actually mix a salad, I guess, but I don't think in this case the boy is talking about mixing salad.
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 khoff's reply was promoted to an answer.