When you find out a girl has already slept with a close
friend. (male or female, it's still
beef)
See Tainted Sausage for a
man.
Dude 1 'Bro I was gona sleep with Chloe, but then I found out you already had'
Dudette 1 'Ah
man that sucks, doesn't matter though, she was tepid at best'
Dude 2 ' When a
friend taints your prospect beef it hurts hard, ahh... Tainted
Beef'