Green’s Dictionary of Slang

chill adj.

[chill (out) v.]

1. [1980s+] (US black) fashionable, chic, ‘with it’.

2. [1980s+] (US black) correct, the real thing.

3. [1980s+] (orig. US black) calm, untroubled, relaxed.

4. [1990s+] (US black) safe.

5. [1980s+] (US black) emotionless, withdrawn, detached.

In compounds

chill pad (n.) [pad n.2 (2)]

[1990s+] (US black) one’s home.

chill (pill) (n.)

[1980s+] (US campus) a metaphorical ‘medicine’ that acts to calm one down; usu. in imper. phr. take a chill pill, relax.