Pertaining to, or originated by, some person named Gregory, especially one of the popes of that name.

Something introduced either by Pope Gregory I from 590-604 A.D., or Pope Gregory III from 1572-85. Gregorian Chant is a ritual plainsong introduced under Pope Gregory I and used in the Roman Catholic Church: it is unharmonized, unaccompanied, and not divided into measures. The Gregorian Calendar is a corrected form of the Julian calendar, introduced by Pope Gregory XIII in 1582 and now used in most countries of the world: it has a 365-day year and a leap year of 366 days every fourth even year.

of or relating to Pope Gregory I or to the plainsong chants of the Roman Catholic Church

Dual-reflector antenna geometry using a concave ellipsoidal subreflector and paraboloidal main reflector.

A dual-reflector antenna system employing a parabolic main reflector and a concave ellipsoidal sub-reflector.