"Declivate" is an uncommon word that means sloping or inclining downwards. There are various synonyms for this word that can be used in different contexts. "Descending" is a common synonym that refers to moving downwards. "Declining" suggests a gradual decrease or fall, while "slanting" implies an oblique angle or tilt. "Sloping," "descending," and "downward" are other synonyms that can be used in place of "declivate" to describe a decline or downward movement. Additionally, "descendent," "drooping," and "slumping" are more specific synonyms that can be used to describe various degrees of declivity.