as in, "what did you say?". sounds tough. Travis Bickle says it in Taxi Driver
Bob: Hey, Charlie.... you're a fucking douche bag
Charlie: What's that?
Something you say when you are embarrassed about something or trying to change the subject.
Adam: "So Dwain I heard you blew that guy last night."
Dwain: "What's that?"
1. Another way of saying "what did you just say?", or asking the speaker to repeat their previous statement, due to lack of volume or attention or volume.
Synonyms: Huh? What? Whu? What did you say?, say again?, you talkin' to me? etc.
2. The question asked by youtube haters, cyber thugs, and internet toughguys when they first see a girl naked at age 45.
1. Matt: "I heard Dave knocked out Bruce last night and took his dope."
Vinnie: (paying attention to something else) "What's that?"
Matt: "I said, I heard Dave knocked out Bruce last night and took his dope."
2. (Paid-up-front-hooker removes her panties before youtube hater)
45 year old Youtube Hater (pointing to the snooch): What's that?
1. Usually used to get an understanding of what someone is seeing. In most cases, the object in question is a face or an animal.
2. What people say when they just can't quite figure out what the hell their looking at.
Jesse: What's that?
Andy: My face.
Another way of saying "what?" or "pardon me"
Synonyms: what, pardon me, say that again, I beg your pardon, I'm sorry?
Person 1- (Says something unintelligible)
Person 2 - What's that?"
Person 1 - I said we should head back now.
Person 2- Oh, alright then