thumbscrew

English Thesaurus

1. screw designed to be turned with the thumb and fingers (noun.artifact)

hypernym	:	screw,
definition	:	a fastener with a tapered threaded shank and a slotted head (noun.artifact)

2. instrument of torture that crushes the thumb (noun.artifact)

hypernym	:	instrument of torture,
definition	:	an instrument of punishment designed and used to inflict torture on the condemned person (noun.artifact)