Fluctuation

Noun

1. A motion like that of waves; a moving in this and that direction; an irregular rising and falling.

   "the fluctuations of the sea"

2. A wavering; unsteadiness.

   "fluctuations of opinion"

3. In medicine, a wave-like motion or undulation of a fluid in a natural or abnormal cavity (e.g. pus in an abscess), which is felt during palpation or percussion.