Definition from Wiktionary, the free dictionary
Formerly a trademark. Most likely from Filipino Ilokano "yóyo"
yo-yo (plural yo-yos)
- A toy consisting of a spheroidal or cylindrical spindle having a circular groove in which string is wound; it is used by holding the string in the fingers and reeling the spindle up and down by movements of the wrist.
- I bought a yo-yo from the toy store yesterday.
- (finance) A volatile market that moves up and down.
- (informal) Someone who vacillates.
- (informal) A foolish, annoying or incompetent person.
- It is hard to watch the management for very long and not conclude that the place is run by a bunch of yo-yos.
someone who vacillates