The Collaborative International Dictionary of English v.0.48:

Lighterman \Light"er*man\ (l[imac]t"[~e]r*m[a^]n), n.; pl.
   Lightermen (l[imac]t"[~e]r*men).
   A person employed on, or who manages, a lighter.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lighterman
    n 1: someone who operates a barge [syn: lighterman,
         bargeman, bargee]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

LIGHTERMAN. The owner or manager of a lighter. A lighterman is considered as
a common Carrier. See Lighters.