PLAGAL

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.