The Collaborative International Dictionary of English v.0.48:

Matross \Ma*tross"\, n. [D. matroos, fr. F. matelot.] (Mil.)
   Formerly, in the British service, a gunner or a gunner's
   mate; one of the soldiers in a train of artillery, who
   assisted the gunners in loading, firing, and sponging the
   guns. [Obs.]
   [1913 Webster]