a spoollike toy consisting of two thick wooden, plastic, or metal disks connected by a dowel pin in the center to which a string is attached, one end being looped around the player's finger so that the toy can be spun out and reeled in by wrist motion.

something that fluctuates or moves up and down, esp. suddenly or repeatedly.

Slang . a stupid, foolish, or incompetent person.

Informal . moving up and down or back and forth; fluctuating; vacillating

yo-yo prices; a yo-yo foreign policy.

Informal . to move up and down or back and forth; fluctuate or vacillate

Mortgage rates are still yo-yoing.

Informal . to cause to yo-yo.