Hissed is a word that describes a sharp, sibilant sound, often made by a snake or angry person. However, there are several other words that can be used as synonyms for hissed, including whispered, murmured, muttered, grumbled, snarled, growled, and spat. Whispered and murmured both imply a softer, quieter sound, while muttered and grumbled suggest a low, indistinct speech. Snarled and growled are typically associated with an animalistic aggression, while spat suggests a forceful, sharp expulsion of air. Ultimately, the choice of synonym will depend on the context in which it is used and the desired tone and connotation of the writing.