adjective

1. designating a mode having a range about a fifth above and a fifth below a control note
2. designating a cadence with the subdominant chord immediately preceding the tonic chord, as in the amen of a religious hymn

Etymology: ML plagalis < plaga, plagal mode < MGr plagios, plagal (in Gr, oblique, slanting) < Gr plagos, a side, akin to pelagos, the sea: see pelagic