A swindler, especially in cards and races. Also, one who works for less than trade-union wages; a non-union workman.
“Pledging the strikers not to return to work so long as a single Black-leg was retained in the service.” —Nineteenth Century, February, 1891, p. 243.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
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