Green’s Dictionary of Slang

greasy adj.1

[fatty food is both tasty and bad for one’s health]

1. (US black) used of something that is simultaneously appalling and appealing.

[US] in E. Cray Erotic Muse (1992) 163: She’s easy, she’s greasy, she works on the street, / And whenever you see her, she’s always in heat.
Ludacris ‘Fatty Girl’ 🎵 I feel greasy when you squeeze me.

2. (US black) duplicitous.

[US]‘Dutch’ ? (Pronounced Que) [ebook] I told you this bitch was greasy! [...] They kidnapped Don!

In phrases

keep it greasy

(US) a phr. of farewell; ‘it’ being a metaphorical vehicle.

[US]Ebonics Primer at www.dolemite.com 🌐 keep it greasey Definition: stay cool, and don’t worry about anything. Example: say my nigga, keep it greasey.
talk greasy (v.)

(US black) to rap smoothly and stylishly.

[US]50 Cent ‘Wanksta’ 🎵 This rap shit is so easy / I’m getting what you get for a brick to talk greasy.

SE in slang uses

In compounds

greasy fingers (n.) [objects ‘stick’ to such fingers]

(US black) a pickpocket.

[[Aus]Bulletin (Sydney) 21 Jul. 10/3: Saw two pickpockets dash into a side-street to investigate a purse one of them had snatched [...]. ‘Well?’ said Lightning-Fingers, peering over Greasy-Hand’s shoulder].
[US]C. Major Juba to Jive.
greasy spoon (n.)

see separate entry.

greasy vest (n.) [the cook’s or waiter’s jacket]

(US) a cheap restaurant or café; a diner.

[US]N. Putnam West Broadway 98: On my word the food ran from ten to fifty cents a portion, and this was no greasy vest, but a snappy little [...] tea room.