Definition of main gauche in US English:

main gauche

(also maingauche, main-gauche)

noun

Fencing
historical
  • A dagger carried in the left hand to parry a stroke or thrust, and used in conjunction with a rapier.

Origin

Mid 19th century; earliest use found in Charles Boutell (1812–1877), writer on heraldry and antiquities. From French main gauche, lit. ‘left hand’ from main hand + gauche left.