Quiescent: Marked by a state of inactivity, repose, or tranquillity. For example, a quiescent stem cell is a stem cell that is resting at the time but that might be stimulated later to divide and proliferate.
Quiescent also means causing no trouble or symptoms. For example, a case of leukemia may be quiescent, causing no problems; the leukemia is in remission and the person has no symptoms of it.
The word "quiescent" comes from the Latin "quiescere", to become silent. Quiescent often suggests a temporary cessation of activity, as in "a quiescent disease."