False relation
A false relation (also known as cross-relation, non-harmonic relation) is the name of a type of dissonance that sometimes occurs in polyphonic music, most commonly in vocal music of the Renaissance and particularly in English music into the eighteenth century. The term describes a "chromatic contradiction" between two notes sounding simultaneously (or in close proximity) in two different voices or parts; or alternatively, in music written before 1600, the occurrence of a tritone between two notes of adjacent chords.