plagal
adjective
pla·gal ˈplā-gəl 
1
of a church mode : having the keynote on the fourth scale step compare authentic sense 4a
2
of a cadence : progressing from the subdominant chord to the tonic compare authentic sense 4b
Word History
Etymology
Medieval Latin plagalis, ultimately from Greek plagios oblique, sideways, from plagos side; akin to Latin plaga net, region, Greek pelagos sea
First Known Use
1597, in the meaning defined at sense 1