Fleche is a fencing
term for a specific type of attack that involves crossing
Typically, when fencers square off they do so with their feet firmly planted apart - all movement is executed while attempting to maintain the distance between feet as much as possible, leaving you with a strong center of balance. A Fleche throws such caution to the wind and turns your attack into a run, more or less.
Typically used to attack from farther away than you would normally be able to, a properly timed Fleche is also an excellent intimidation tactic - the mental being as important (if not more so) as the physical when fencing.
Crossing your feet is strictly illegal when fencing Sabre, so the Fleche is also a no no.