It sounds like "what's that mean" but it's actually the word "does" said very fast : "what DOES that mean" and it sound more like ""whatiz" that mean?" So it's perfect if you say it like this but you should never write it with the contraction because "does" can not be contracted in the written language.

If you say "what does" very very fast, it sounds like "what's". Other examples: Wherez he live? Whats he do? ...and a few more.

"What's that mean?" is short for "What does that mean?". "What does that mean?" and "What does it mean?" have the same meaning but are used differently. Remember the difference in using "it" and "that". "What does that mean?" is used when referring to what someone else/the person you are talking to said. Person A: I hate people who bamboozle? Person B: What does that mean? Person A: It means i hate people who cheat. Here, 'that' referred to what Person A said. "What does it mean?" is used when referring to something you have said. You: I read that he was hit by descending timber. What does it mean? Person B: It means he was hit by a falling tree. Here, "it" refers to what you said in the previous sentence. In a formal business situation, use the full form "What does that mean?" instead of the abbreviated form "What's it mean?" Also remember that you will use "What does that mean?" only when referring to what someone else has just said. If you repeat what someone else has said or read an excerpt from a book or passage, you should use "What does it mean?" instead. A safer way is to simply use the phrase you want to clarify in place of it/that. What does descending timber mean? This is more straightforward and to the point. Also, it is more likely that you will use "What do you mean?" in a business situations. This is used when you want the person to explain what he has said or elaborate on his point.

what it be meanin' brutha?

What does it mean What does that mean I prefer this form