Green’s Dictionary of Slang

nasty adj.

[on bad = good model or fig. use of SE nasty]

1. [mid-19C+] (orig. US) first-class, exciting, particularly enjoyable or admirable.

2. [mid-19C+] (orig. US) attractive, sexy; often in negative sense, i.e. promiscuous, amoral.

3. [mid-19C+] (orig. US) aggressive, hostile, bad-tempered.

4. with ref. to speech or writing, sexually suggestive (whether explicitly or not).

5. [1980s+] (orig. US) difficult.

6. [1990s+] (W.I./UK black) dirty.

In compounds

nasty-ass (adj.) (also nasty-assed) [1960s+] (US)

1. of a person, unpleasant.

2. of a place, thing or animal, dirty, disgusting.

nasty-behind (adj.)

[1960s] (US black) of a female, promiscuous.

nastygram (n.)

[1960s+] (US, orig. milit.) an unpleasant note or letter or a communication that brings bad news.

nastyman (n.)

1. [mid–late 19C] the member of the garrotting team who actually does the choking.

2. [late 19C] (UK Und.) a thief’s assistant.

3. [1950s–60s] (US black) a sexual pervert.

nasty-mouthed (adj.)

[20C+] (W.I.) foul-mouthed, given to using obscene language.

nasty nigger (adj.)

[1990s+] (W.I.) ill-mannered, boorish.

In phrases

nasty up (v.)

[20C+] (W.I.) to make a mess of, to dirty.