Noun
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.
A descending surface; a sloping place.
Source: Webster's dictionaryThe town was built on the southern declivity, and was surrounded by a wall, which, allowing for the natural irregularities of the soil, represented a triangle, with the castle at the summit—a form observable in many of the ancient cities of Greece. Source: Internet
When he walked, he walked as though he went down a declivity. Source: Internet