Oscillate, v. i. [imp. & p. p. Oscillated; p. pr. & vb. n. Oscillating.]
Etymology: [L. oscillare to swing, fr. oscillum a swing, a little mask or puppet made to be hung from trees and swing in the wind, prob. orig., a little mouth, a dim. from os mouth. See Oral, and cf. Osculate.]
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.
Shades of meaning
Fernald has no entry of its own for oscillate; he lists it under fluctuate, shake.
Where he writes about it:
A thing rocks that is sustained from below; it swings if suspended from above, as a pendulum, or pivoted at the side, as a crane or a bridge-draw; to oscillate is to swing with a smooth and regular returning motion; a vibrating motion may be tremulous or jarring. — from shake
The pendulum of a clock may be said to swing, vibrate, or oscillate; a steel bridge vibrates under the passage of a heavy train; the term vibrate is also applied to molecular movements. — from shake