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
OSCILLATEstresses a usually regular alternation of direction. an oscillating fan VIBRATEsuggests the rapid oscillation of an elastic body under stress or impact. the vibratingstrings 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
UNDULATEsuggests a gentle wavelike motion. an undulating sea of grass