Oscillation /(?)/

Os·cil·la·tion

Oscillation

n.
  1. The act of oscillating; a swinging or moving backward and forward, like a pendulum; vibration.
  2. Fluctuation; variation; change back and forth.
    His mind oscillated, undoubtedly; but the extreme points of the oscillation were not very remote.

Phrases & Compounds
Axis of oscillation
See under Axis, and Center.