declivity

n.; pl. Declivities [ L. declivitas, fr. declivis sloping, downhill; de + clivus a slope, a hill; akin to clinare to incline: cf. F. déclivité. See Decline. ] 1. Deviation from a horizontal line; gradual descent of surface; inclination downward; slope; -- opposed to acclivity, or ascent; the same slope, considered as descending, being a declivity, which, considered as ascending, is an acclivity. [ 1913 Webster ]

2. A descending surface; a sloping place. [ 1913 Webster ]

Commodious declivities and channels for the passage of the waters. Derham. [ 1913 Webster ]