noun, plural de·cliv·i·ties.
- a downward slope, as of ground (opposed to acclivity).
noun plural -ties
- a downward slope, esp of the groundCompare acclivity
1610s, from French déclivité, from Latin declivitatem (nominative declivitas) “a slope, declivity,” from declivis “a sloping downward,” from de- “down” + clivus “a slope,” from PIE *klei-wo-, suffixed form of *klei “to lean” (see lean (v.)).