In fencing, a call to adopt a defensive stance in readiness for an attack or bout (2,5)

(Other definitions for en garde that I've seen before include "The opening position in fencing - mind yourself" , "(In fencing) in a defensive stance" , "French opening position in fencing - protect yourself" , "Angered with opening position in fencing - be alert. (2,5)" , "Prepare to fence!" .)