Webster's Revised Unabridged Dictionary · 1913

Acclivity

Acclivity ({not transcribed}) , noun

[Latin acclivitas, from acclivis, acclivus, ascending; ad + clivus a hill, slope, from root kli to lean. See Lean.]

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.