a toy consisting of a pair of joined discs with a deep groove between them in which string is attached and wound, which can be spun alternately downward and upward by its weight and momentum as the string unwinds and rewinds

with a flick of the wrist, she sent the yo-yo spiraling down and watched it spin there

a person who is stupid or dangerously unpredictable

they think they're tangling with some small-town yo-yos, but they're not

move up and down; fluctuate

popularity polls yo-yo up and down with the flow of events