Green’s Dictionary of Slang

1. a failure, an incompetent, a novice, an oaf.

1886		Nat. Police Gaz. (NY) 15 May 14/2: Some of the teams which are now considered ‘dubs’ will come right up to the front.
1896		Ade Artie (1963) 4: What kills me off is how all these dubs make their star winnin’s.
1906		S. Ford Shorty McCabe 146: I’m nothin’ but a dub at anything like that.
1908		‘O. Henry’ ‘Conscience in Art’ in Gentle Grafter (1915) 133: The pawnbroker [...] thinks it was soaked by some Arabs or Turks or some foreign dubs.
1915		Drew & Evans Grifter 9: ‘I know I’m a big dub [...] I ought to be kicked over the market buildings’.
1917		F. Packard Adventures of Jimmie Dale (1918) I xi: Twice I tried to get this old dub’s coin out here, and couldn’t find it.
1920		B. Cronin Timber Wolves 254: Why, you poor dubs, did you think you could get to windwards of a man like Sam Frame?
1922		S. Lewis Babbitt (1974) 42: Like a lawyer defending a client – his bounden duty, ain’t it, to bring out the poor dub’s good points?
1937		J. Tully Bruiser 27: On an ‘off night’ a champion might lose to a dub.
1947		B. Schulberg Harder They Fall (1971) 105: Even when he was a dub he was always dangerous.
1953		T. Runyon In For Life 34: I was a dub at all other card games.
1967–8		Baker et al. CUSS 110: Dub A person who always fools around.
1989		M. Amis London Fields 381: He was afraid he had been rather a dub with Keith’s harem; most awkward; they had all seemed to look right through him.
1996		H. Roth From Bondage 234: Leo was the worst dub at plane geometry Ira had ever known.

2. something that fails, a disaster; also attrib.

1889

World (N.Y.) 20 Oct. 2/2: His slide [...] gave Richardson the chance to touch him out after Ewing had made a dub throw.