Wordnet 3.0
NOUN (1)
1. 
 the foreman of a work gang; 
The Collaborative International Dictionary of English v.0.48:
Ganger \Gang"er\, n.
   One who oversees a gang of workmen. [R.] --Mayhew.
   [1913 Webster]
WordNet (r) 3.0 (2006):
ganger
    n 1: the foreman of a work gang