1. "It sucks!" or, with less vulgarity, "It stinks!" both mean that something is very bad. 2. "That's tough!" can mean several things. It can mean "That's difficult!" or "That's a very difficult problem!" It can also mean "That's very unfortunate, but I don't care. You'll have to accept things as they are." "It's cool" or "It's neat" means "It's good, intriguing, interesting".