Pla"gal (?), a. [F., from Gr. 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.
© Webster 1913.