Acclivity :: Acclivity (n.) A slope or inclination of the earth, as the side of a hill, considered as ascending, in opposition to declivity, or descending; an upward slope; ascent..
Declivity :: Declivity (n.) 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..
Declivity :: Declivity (n.) A descending surface; a sloping place.