Synonyms of declivity
declinationthe angular distance, esp in degrees, of a star, planet, etc, from the celestial equator measured north (positive) or south (negative) along the great circle passing through the celestial poles and the body
descentA descent is a surface that slopes downwards, for example the side of a steep hill.
• On the descents, cyclists freewheel past cars.
inclineAn incline is land that slopes at an angle.
• He came to a halt at the edge of a steep incline.
Thesaurus for declivity from the Collins English Thesaurus
a downward slope, esp of the ground