Definition of plein jeu in US English:

plein jeu

adverb

Music
  • Chiefly as a direction in a score: with full power (specifically in organ playing).

noun

Music
  • An organ stop or combination of stops producing a full chorus of montres (diapasons and principals) in octaves, plus fourniture (additional mixture pipes, adding fifths), and sometimes cymbal.

Origin

Mid 19th century. From French plein jeu organ stop that has a very loud sound, a type of mixture stop combining the fourniture and the cymbal from plein + jeu.