IPA: /θʌmzˌkruː/
KK: /θʌmzˌkru/
A type of screw that can be easily turned by hand, often used for fastening things together or as a tool for torture in the past.
The carpenter used a thumbscrew to secure the wooden pieces together.
Thumbscrew → The word is formed from "thumb" (from Old English "þuma", meaning the short, thick digit on the hand) and "screw" (from Old French "escroue", meaning a device for fastening). A thumbscrew is a device that is operated by the thumb, typically used for tightening or securing something.
Think of using your 'thumb' to operate a 'screw' — that's how a thumbscrew works.
No commonly confused words.