fluctuate

swing, sway, oscillate, vibrate, fluctuate, waver, undulate mean to move from one direction to its opposite. swing implies a movement of something attached at one end or one side.

• • the door suddenly swung open

sway implies a slow swinging or teetering movement.

• • trees swaying in the breeze

oscillate stresses a usually regular alternation of direction.

• • an oscillating fan

vibrate suggests the rapid oscillation of an elastic body under stress or impact.

• • the vibrating strings of a piano

fluctuate suggests constant irregular changes of level, intensity, or value.

• • fluctuating interest rates

waver stresses irregular motion suggestive of reeling or tottering.

• • the exhausted runner wavered before collapsing

undulate suggests a gentle wavelike motion.

• • an undulating sea of grass