1-Basically meaning that's really shit, or that isn't good, that's ass is terribly underused in modern day society. People who do use it, use it to express their anger or saddness for a certain event, like running out of beer.
2-Expressing one's feeling for someone telling a lie about a certain event, like running out of beer.
3-Taking notice of someone's ass, and thinking it is good, probably while you're under the infulence of beer.
1-Bill-Yo, dude pass me another can.
Bob- I can't, Ben over there drank it all.
Bill-That's ass, Ben, WHY?
2-Bill-Yo, dude pass me another can.
Bob-I can't, Ben over there drank it all.
Ben-That's ass, why lie.
3-Bill-Hey dude, look at that ass there.
Bob-Now that's ass.
Ben-I want some.