'master-at-arms' definitions:

Definition of 'master-at-arms'

(from WordNet)
noun
The senior petty officer; responsible for discipline aboard ship

Definition of 'master-at-arms'

From: GCIDE
  • master-at-arms \master-at-arms\ n. (Naut.) The senior petty officer of a ship, responsible for discipline aboard the ship. [WordNet 1.5]