Green’s Dictionary of Slang

1. relaxation, a rest; also attrib.

1955		‘Blackie’ Audett Rap Sheet 86: Then me and Al taken off for a cool-out spot in Illinois.
1998		Source Nov. 105: A half-hour cool-out from taping Erykah Badu’s ‘Next Lifetime’ video.

2. (US drugs) a period of abstention from drug use; also attrib.

1997

L. Pettiway Workin’ It 186: She lets me stay in her house if I come in and that’s my cool-out period.