Green’s Dictionary of Slang

1. to disappoint, to depress, to disturb.

1970		D. Mitchell Thumb Tripping (1971) 22: We’re fucking with his head, don’t you see? What if something bums him, Chay?
1970		Frank Zappa ‘Rudy Wants To Buy Yez A Drink’ 🎵 I carry a gun / I hope the bulge / Don’t bum you out.
1977		L. Bangs in Psychotic Reactions (1988) 232: Having bummed out almost the entire population of one room, I took my show into another.
1986		H.B. Gilmour Pretty in Pink 107: I’m sorry about bumming out the night for you.
1994		G. Indiana Rent Boy 53: I realized it really bummed me out having customers invading my living space.
2000		M. Manning Get Your Cock Out 35: That hallucinatory medics would drag the collapsed and bloody debauchees into another room so as not to bum out the rest of the high lifers.
2011		Big Issue (Cape Town) 10 Jan. 19/1: Does music piracy bum you out.
2015		Baltimore Sun (MD) 25 Feb. T23/1: ‘It bums me out that you realize it’s just a baby’.

2. to be disappointed, to be depressed.

1977		C. McFadden Serial 68: Who’d tried jogging and bicycling but rapidly bummed out on watching her knees go up and down.
1996		Eble Sl. and Sociability 30: In college slang out is the most productive particle: [...] bum out ‘cause or experience unpleasant feelings or bad reactions’.
2010		(con. 1973) C. Stella Johnny Porno 171: Nick was bummed from her lack of enthusiasm.
2020		C. Hiaasen Squeeze Me 184: ‘He was bummed the pearls didn’t get here in time for Valentine’s Day’.

3. (US campus) to fail a test.

1970

Current Sl. IV:2 4: Bum out, v. To fail a test.