Sibilating is a word that is often used to describe a particular sound made by snakes or other reptiles as they slither or move about. Some synonyms for this word might include hissing or whispering, as both of these terms suggest a certain level of quietness or subtlety in the sound being made. Other possibilities might include whispering, murmuring, or rustling, all of which suggest a similar kind of soft, almost secretive sound. Ultimately, the choice of synonym depends on the context in which the word is being used, as well as the intended tone and meaning of the sentence in which it appears.