Movable
MOVABLE, adjective [from move.] That may be moved; that can or may be lifted, carried, drawn, turned or conveyed, or in any way made to change place or posture; susceptible of motion.
1. That may or does change from one time to another; as a movable feast.
A movable letter, in Hebrew grammar, is one that is pronounced, as opposed to one that is quiescent.