An agreement - 'True, that'. A modern day amen, if you like.
"That girl there is arousing"
(Pronounced: "True-dat") 1. Slang for "True that," meaning "That is true."; 2. an affirmation by one bro to another bro on a statement; 3. while perhaps not THE truth, an agreement with a homie's opinion, whether it be a like or dislike; 4. Another version of the word ssrite.
MC: "Sup, my brutha? Dis new recawd iz off tha chain!!!"
DJ: "Trudat! Itz da bomb. No way those boyz puttin' out sumpthin' whack."