Green’s Dictionary of Slang

out to lunch adj.

[i.e. ‘not all there’]
(orig. US campus)

1. crazy, eccentric, weird.

[US]N.Y. Herald Trib. 15 Mar. IV 1/2: You want to dust a guy off lightly but thoroughly? ‘That guy is strictly out to lunch.’ That’ll put him in his place.
[US]G. Swarthout Where the Boys Are 217: I know it’s out to lunch for a girl to be willing to wait five minutes these days.
[US](con. 1950s) H. Junker ‘The Fifties’ in Eisen Age of Rock 2 (1970) 102: She would certainly be turned off if he were [...] out to lunch.
[US]R. Price Ladies’ Man (1985) 32: They wanted a freak show. They wanted back all the people who were either so out to lunch or so atrocious.
[US]T. Wolfe Bonfire of the Vanities 575: This kid is out to lunch.
[UK]Guardian 11 Nov. 5: Signed a card to one of her pupils ‘Miss Ren Out To Lunch And Out Of Her Head’.
[US]W.T. Vollmann Royal Family 624: You think I’m out to lunch, don’t you? You think I’m crazy.

2. in a daze, stupid, naïve.

[US]Wash. Post 29 Sept. F1/1–2: Of course, ‘lunching’ is the opposite of O.T.L. (out to lunch) which plainly tells you that someone is out-of-it, not-in-the-groove, or not-with-it.
[US]F. Kohner Gidget Goes Hawaiian 4: In case you’ve been out to lunch, Father, being pinned means you’re on your way to your real honeymoon.
[US]E. Torres Carlito’s Way 109: I must be out to lunch in my skull.
[US]Eble Campus Sl. Mar. 5: out to lunch – failing to recognize the reality of a situation.
[UK]J. Morton Lowspeak 109: Out to lunch [...] 2. totally in the wrong.

3. seen as alien to the peer group.

[US]Baltimore Sun (MD) Sun. Mag. 4 Dec. 9/1: ‘Am I out to lunch?’ she asked a straight man. ‘Am I all filter? How did I get into this Vancouver bit?’.
[US]Current Sl. III–IV (Cumulation Issue) 89: Out to lunch, adj. [...] a person who does not take drugs.
[US]Current Sl. III:4 8: Out to lunch, adj. Conceited, snobbish.

4. absent, unavailable.

[US]O. Hawkins Ghetto Sketches 118: I was goin’ through one of those deep money slumps . . . luck was out to lunch.

5. intoxicated by drink or drugs; feeling very happy.

[US]A. Young Snakes (1971) 34: It’s my thing, jim! I be’s out to lunch! I’ll play me some LPs and shit and maybe smoke me some charge.
[UK]Observer Mag. 11 June 17: Andrew got fed up with him being ‘fucking out to lunch’.