siss Get Printable Handwriting Hear It! Say It! Write It! Learn It! Spelling Test Definition verb. to make a hissing sound like a snake. Example Sentence He is such a siss. More Example Sentences He heard a siss from the bushes. Synonyms hiss; whisper; sibilate Antonyms brave; strong Hear It! Say It! Write It! siss Switch to cursive Start Share with your friends: