thumbscrew
nounA screw designed so that it can be turned with the thumb and fingers.
An instrument of torture formerly used to compress the thumb.
A screw having a broad head, or a plate projecting from the head, so that it may be turned easily by the finger and thumb.
An instrument of torture by which one or both thumbs were compressed so as to inflict great agony without danger to life.
A screw having a flat-sided or knurled head, so that it may be turned by the thumb and forefinger.
