Plā'gal, a.

a. [Fr. plagal, from Gr. πλάγιος, sidewise, slanting.] (Mus.) Having the principal tones lying between the fifth of the key and its octave or twelfth;—said of certain melodies or tunes, and opposed to authentic.

Plagal cadence, a cadence in which the final chord on the tonic is preceded by the chord on the subdominant.