A missile was a self-propelled projectile used as a weapon.
The ones used by spacefaring human civilizations after the Hiatus were basically miniature starships with only a High Drive for propulsion. Modern antiship missiles had no explosive warhead whatsoever, depending solely on the kinetic energy of their impact on the target.1:3
Plasma cannons were used to deflect incoming missiles by vaporizing portions of the projectile and converting the affected mass into slewing thrust.2:1
The converters that turned the missile's fuel—water—into anitmatter were expensive. Most nations used single-converter units: they had the same terminal velocity as the weapons in front-line service with the RCN and the Alliance Fleet, but they took twice as long to accelerate. Navies which expected to use their missiles—and who could afford them—equipped their ships with dual-converter models, thereby gaining an advantage in combat.8:8