A fusillade is the simultaneous and continuous firing of a group of firearms on command. It stems from the French word fusil, meaning firearm, and fusiller meaning to shoot.
In the context of military tactics, the term is generally used to refer to a type of organized and concentrated gunfire from a military unit armed with small arms, and initiated by a command from a commanding officer. The term can also be used as a verb, as in "to fusillade an enemy position". Suppressing fire (done in conjunction with fire and movement) is often in the form of a fusillade.
In non-military contexts, a fusillade is used to mean a sudden flurry or outburst of activity directed at something, such as "a fusillade of questions".