Pla″gal (plā″gal), a. [F., from Gr. πλάγιοσ sidewise, slanting.] (Mus.) Having a scale running from the dominant to its octave; — said of certain old church modes or tunes, as opposed to those called authentic, which ran from the tonic to its octave.
Plagal cadence, a cadence in which the final chord on the tonic is preceded by the chord on the subdominant.