Thumbscrew

[Little_Girl]

A screw having a flat-sided or knurled head, so that it
may be turned by the thumb and forefinger.

[Jason Yan]

noun:
A torture device of many forms and shapes. The main purpose it serves is to inflict slow and excrutiating pain to the fingers or toes of a victim.

verb:
A sexual technique involving [the thumb] (or both thumbs) to screw or fuck their partner or victim. Usually performed in the [thumbs up] or [handshake] position.

[Tanya Shivari]

A [way] for an [inquisitor] to [have fun].

[Little_Girl]

An instrument of torture for crushing the thumbs.

[Mark Zuckerberg]

a device used especially in the past to torture people (= cause them great pain) by crushing their thumbs