Green’s Dictionary of Slang

ill adj.

[fig. uses of SE ill, unwell]
(US black/teen)

1. angry, frustrated; of an animal, vicious.

[US]F.L. Olmsted A Journey Through Texas 78: ‘Ill,’ for ‘vicious.’ ‘Is your dog ill?’.
[US]J.W. Carr ‘Words from Northwest Arkansas’ in DN III:i 83: ill, adj. Cross ‘The dog’s ill’.
[US]Eble Campus Sl. Mar. 4: ill – angry, annoyed.
[US]Ebonics Primer at [Internet] ill Definition: to be ugly, fucked up or wrong. Example: Yo son, hoe be ill, you best ditch da bitch.
[US]C. Eble (ed.) UNC-CH Campus Sl. 2011 6: ILL — rude, angry, in a bad mood: ‘Nicholas was ill all day after his fight with Courtney’ .

2. aggressive, offensive, bad.

[US]Sugar Hill Gang ‘Rapper’s Delight’ [lyrics] A time to break and a time to chill / to act civilized or act real ill.
[US]Ice-T ‘Heartbeat’ [lyrics] Try to get ill and serve you boy.
[US]Dr Dre ‘Murder Ink’ [lyrics] Resume the wifey boo shit, cause yo my man don’t know / that his bitch is straight ill, servin ass with fo’fo’.
[UK]Guardian Guide 1–6 Jan. 17: You gotta name pit bulls ill names like Killer or Bitch. Call it Daisy? Not a pit bull.

3. (also illy) on the bad = good model, wonderful, first-rate.

[US]C.I.A. ‘My Posse’ [lyrics] Crenshaw is where I chill, / Never ever sick but always ill.
[US]LL Cool J ‘.357 – Break It On Down’ [lyrics] Illy ill fire-starter hittin harder than King Kong.
[US]Tribe Called Quest ‘Baby Phife’s Return’ [lyrics] Represent the Zulu Nation with illy rap creations.
[US]Source Oct. 22: Bone has [...] proved themselves to be the illest and most unique rap group out today.
[US]‘Touré’ Portable Promised Land (ms.) 161: We Words (My Favorite Things) [...] Baad. Ill. Dope.
[US]LL Cool J ‘After School’ [lyrics] Body so illy she make a grown man silly.
[UK]A. Wheatle Dirty South 52: His older brother’s got an ill ride.
[US]J. Díaz This Is How You Lose Her 97: My brother had never been the most rational of agents but this one was the ill zinger.

4. unattractive.

[US]Eble Campus Sl. Apr.

In exclamations

that’s so ill!

(US teen) an all-purpose denunciation of an object or activity. 9 July [Internet] Wut! That’s so ill! Congrats.

SE in slang uses

In compounds

ill music (n.)

see separate entry.