Answer: stillest

AnswerCrossword Clue
STILLESTLeast disturbed.
STILLESTMost peaceful.
STILLESTMost quiet
STILLESTMost stationary
stillest(of air or water) Undisturbed by wind, sound, or current; calm and tranquil
stillestNot moving or making a sound
stillestSTILL, free from sound or motion
stillest(of a drink) Not effervescent