1. Disgustingly stinky and unpleasant to the extreme: There was a nasty smell coming from the sewer out on the street.

The medicine left a nasty taste in Bill's mouth.

2. Improper, disgusting, X-rated: When Ronda turned the TV set on at the motel, she was shocked to see the nastiest videos she had ever imagined possible, which also included a lot of nasty language.
3. Disagreeable, bad tempered, and critical: He played a nasty trick on her for revenge because she had refused to go out with him.

Jerry called Karin some of the nastiest things that Shelby had ever heard, but she called him a few that were even nastier and hurriedly walked away.

4. Irritating, unpleasant, or difficult: The nasty rain storms made it impossible for Greg and Shawn to go on the trip as they had planned.
5. Unpleasant, mean spirited, or dangerous: The nasty accident injured several students; especially, the one who had one of the nastiest bumps on his head that the doctor had ever seen.
6. Exasperating, and excessively difficult to solve or to handle: The paper presented a very nasty puzzle which was impossible to solve, but Bill's friend told him that there had been an even nastier the week before.