Phrase: best way ever to piss people off and get them irate in a matter of minutes. It can be used at any time, with any statement anywhere and will cause instant confusion, good times will ensue. It is best especially if you never tell the other person why you said it, and just keep repeating the phrase over and over again. It's sure to make anyone feel insecure about what they just said, and they will think that you took what they said to mean something sexual probably, even if it's the most random thing ever.

A verbal prank commonly used by in a conversation, with the intent of annoying the listener. In this prank, there are two parties having a conversation: person A (the pranked) and person B (the pranker). Person A makes a simple, innocent remark with no double meanings. Person B initiates the prank and replies, "I know what THAT means" (note the emphasis on the word "that").

The prank is that person A begins to feel insecure or uncomfortable about what they have said, because the phrase, "I know what THAT means" gives the impression that person B misunderstood what was said (i.e. thinks it has a sexual meaning, or thinks they're lying about something). Person A is completely unaware that person B is just trying to annoy them.

After this, person B could proceed to only say, "I know what THAT means."