Oscillate

Part of speech: verb (v.)

1. To move backward and forward; to vibrate like a pendulum; to swing; to sway.

2. To vary or fluctuate between fixed limits; to act or move in a fickle or fluctuating manner; to change repeatedly, back and forth. The amount of superior families oscillates rather than changes, that is, it fluctuates within fixed limits. Dc Quincey.