whirligig

Short definition from Wiktionary

Noun

1. 1
   Anything that whirls or spins around, such as a toy top or a merry-go-round.
2. 2
   A device incorporating spinning, wind-driven propellers or pinwheels, used as whimsical outdoor decoration in a garden or on a porch.
3. 3
   Ellipsis of whirligig beetle.
4. 4
   A device for punishing prisoners, comprising a wooden cage that rapidly spins around to induce nausea.