(1):

(a.) Being in a state of repose; at rest; still; not moving; as, a quiescent body or fluid.

(2):

(a.) Not sounded; silent; as, y is quiescent in "day" and "say."

(3):

(n.) A silent letter.

(4):

(a.) Not ruffed with passion; unagitated; not in action; not excited; quiet; dormant; resting.