Green’s Dictionary of Slang

1. (US campus) living as an idler or loafer.

1860		Yale Literary Mag. XXV 308: Another great shame connected with our social life is that of spreeing or ‘bumming’ [DA].
1891		Bird o’ Freedom (Sydney) 28 Mar. 4/3: Can Anybody Tell Us [...] How much ‘bumming’ a pro can do when he is really put to it?
1929		E. Booth Stealing Through Life 152: Just bumming around gets awfully tiresome.

2. (US) living as a vagrant tramp or hobo.

1857		S.F. Call 9 Jan. 1/2: The ‘Bumming and Gassing Company’ were out in full strength, the novelty of labor being a new experience [DA].
1870		Appleton’s Journal (N.Y.) 30 Apr. 497/1: It could be no worse than ‘bumming,’ i.e., sleeping out.
1891		C. Roberts Adrift in America 66: The idea of begging, or ‘bumming,’ as it is popularly called out there, went strongly against my stomach.
1899		J. Flynt Tramping with Tramps 137: It ain’t work that makes blokes hungry; it’s bummin’!
1916		‘A-No. 1’ Snare of the Road 11: The job I made of box car bumming proved so eventless.
1935		N. Algren ‘A Place to Lie Down’ in Texas Stories (1995) 58: Bummin’ takes all the tallow out o’ mah pole.

3. (US campus) relaxing.

1997–2000

Da Bomb 🌐 5: Bummin’: Staying at home, relaxing.

4. (US teen) dressing unfashionably.

1997

Springfield (MA) Union-News 9 Sept. C6/5–6: bummin’—To dress in a very tacky way.