Definition of King's X in English:

King's X

Pronunciation /ˌkɪŋz ˈɛks/

noun

US
  • A truce term called out (especially in children's games, such as tag) to claim a respite or exemption, typically accompanied by crossed fingers.

exclamation

US
  • Especially in children's games: used to call for a truce or claim temporary immunity from capture, etc., typically accompanied by crossed fingers; ‘Truce!’; ‘Time out!’.

Origin

Late 19th century; earliest use found in Modern Language Notes. From the genitive of king + X, apparently with reference to the gesture of crossed fingers which usually accompanies the calling out of the term.