'G-man' definitions:

Definition of 'G-man'

(from WordNet)
noun
A special law-enforcement agent of the Federal Bureau of Investigation [syn: G-man, FBI agent, government man]

Definition of 'G-man'

From: GCIDE
  • G-man \G-man\ n. [from Government man.] A special law-enforcement agent of the Federal Bureau of Investigation.
  • Syn: FBI agent, FBI man, government man. [WordNet 1.5]