Green’s Dictionary of Slang

1. unexcited (in a sexual context).

1970

(con. 1950s) H. Junker ‘The Fifties’ in Eisen Age of Rock 2 (1970) 102: She would certainly be turned off if he were grubby.

2. out of touch, unaware, daydreaming.

1961

Metronome Feb. 30: I am one of those who got turned off a couple of years ago when Brookmeyer started recording albums that sounded like trumped-up dixieland.

3. (US campus) unenthusiastic.

1967–8		Baker et al. CUSS 214: Turned off Not eager for or looking forward to something, someone. Disgusted.
1973		L. Bangs in Psychotic Reactions (1988) 121: Responsible people all over were so turned off by this pic.