Webster's Revised Unabridged Dictionary · 1913

Quiescent

Quiescent , adjective

[Latin quiescens, -entis, present participle of quiescere: compare French quiescent. See Quiesce.]

1.
Being in a state of repose; at rest; still; not moving; as, a quiescent body or fluid.
2.
Not ruffed with passion; unagitated; not in action; not excited; quiet; dormant; resting.
In times of national security, the feeling of patriotism... is so quiescent that it seems hardly to exist. — Prof. Wilson
3.
(Grammar) Not sounded; silent; as, y is quiescent in “day” and “say.”

Quiescent , noun

(Grammar) A silent letter. — M. Stuart