1. physically filthy; disgustingly unclean: a nasty pigsty of a room.
2. offensive to taste or smell; nauseating.
3. offensive; objectionable: a nasty habit.
4. vicious, spiteful, or ugly: a nasty dog; a nasty rumor.
5. bad or hard to deal with, encounter, undergo, etc.; dangerous; serious: a nasty cut; a nasty accident.
6. very unpleasant or disagreeable: nasty weather.
7. morally filthy; obscene; indecent: a nasty word.
8. Slang.formidable: The young pitcher has a good fast ball and a nasty curve.