Green’s Dictionary of Slang

1. passive, relaxed, casual.

1971		E.E. Landy Underground Dict. (1972).
1977		C. McFadden Serial 9: She [...] concentrated on her mantra until she was feeling laid back again.
1985		R.G. Barrett You Wouldn’t Be Dead for Quids (1989) 205: Being a laid-back married man with five kids he loved nothing better than a bit of gossip.
1987		G. Wolff ‘A Day at the Beach’ in A Day at the Beach (1992) 134: But, my God, Nicholas was edgy, the laid-back one, a grace-under-pressure boy.
1998		G. Burn Happy Like Murderers 65: They were both so stoned. So laid back that they were horizontal, was that what they used to say?
1998		Hip-Hop Connection Dec. 16: The other bus is for the more laidback members of the group.
2000		W. Shaw Westsiders 55: Khop’s style is laid-back, but his delivery is confident.
2003		Simon & Burns ‘Hard Cases’ Wire ser. 2 ep. 4 [TV script] ‘You know what subtle means?’ ‘Laid-back and shit’.
2009		R. Milward Ten Storey Love Song 179: Johnnie [...] seems much more laid-back [...] beaming and bouncing along.

2. of music, soothing, peaceful.

1974

Eble Campus Sl. Mar. 4: laid-back – referring to music, a mellow creation.

3. intoxicated by drugs or alcohol.

1976		Eble Campus Sl. Nov. 3: laid back – relaxed to the point of almost total immersion in a dream world, usually because of drink or drugs.
1993		Snoop Doggy Dogg ‘Gin and Juice’ 🎵 Rollin down the street, smokin indo, sippin on gin and juice / Laid back.