A derogatory phrase used to berate or otherwise castigate another male as to make him feel inferior to other males or to put him in his place. This phrase almost always alludes to the other male as belonging to a different sexual orientation (ie homosexual). This phrase is usually uttered in a heated conversation.
Listen you F**king Cum Stain. Why don't you go suck another couple hundred cocks before you try to run off at the mouth to me. Do you know who I am?
A cum-stained futon (or CSF) is what you find in the home of a low-class loser who is always at home beating off on his futon. It is stained with his semen (cum) drops.
it a derogatory to example what an ass or bitch your being like a guy who miss the chick's mouth when he was cuming and let her past out with the cum still on her upper lip.