Tom: Have you seen the new Star Wars movie yet?
Jim: Yeah, I saw it last night. It was so sick!
Tom: I know! I think it is the best one yet.
Sara: On Saturday we went to the street skateboarding championships, and it was so cool!
Kim: I bet! I can't believe so of the tricks that they can do now.
Sara: I know! We saw some really sick tricks.
Meaning: "sick" is an idiom/slang word that is used to describe something that is really cool.