1. Physics. a. the velocity at which a falling body moves through a medium, as air, when the force of resistance of the medium is equal in magnitude and opposite in direction to the force of gravity.
b. the maximum velocity of a body falling through a viscous fluid.
2. Rocketry,Ballistics. a. the greatest speed that a rocket, missile, etc., attains after burnout or after leaving the barrel of a gun.
b. the speed of a missile or projectile on impact with its target.