A downward slope or declivity; a gradual descent or decline of terrain.
From Latin declivis, meaning 'sloping downward.' This is a somewhat archaic term for a slope or downward grade.
This word is practically extinct in modern English, preserved mainly in geology and landscape descriptions, but it's the root of 'declivity'—which explains why historical maps used 'declive' to mark steep hillsides.
Complete word intelligence in one call. Free tier — 50 lookups/day.