—adj. 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.
—n. Informal.a nasty person or thing.
a combining form with the meaning “nastic pressure,” of the kind or in the direction specified by the initial element: hyponasty.