armament consisting of a long cylindrical self-propelled underwater projectile that detonates on contact with a target
a small explosive device that is placed on a railroad track and fires when a train runs over it; the sound of the explosion warns the engineer of danger ahead
a small firework that consists of a percussion cap and some gravel wrapped in paper; explodes when thrown forcefully against a hard surface
an explosive device that is set off in an oil well (or a gas well) to start or to increase the flow of oil (or gas)
marked by qualities giving the power to produce an intended effect; "written propaganda is less efficacious than the habits and prejudices...of the readers"-Aldous Huxley; "the medicine is efficacious in stopping a cough"