declivity[noun]Synonyms: descent, decline, dip, drop, fall
Antonyms: acclivity
 [TahlilGaran] English Synonym Dictionary ▲
 declivity noun. 
[dɪ'klɪvɪti] E17.[Latin declivitas, from declivis sloping down: see DECLIVE adjective, -ITY.]1.  Downward slope, inclination. 
E17.2.  A downward slope, sloping ground. 
L17.  [TahlilGaran] English Dictionary ▲