siss vs emit

siss and emit both are verbs.

Word	Noun	Adjective	Verb	Adverb
siss	No	No	Yes	No
emit	No	No	Yes	No

As verbs, emit is a hypernym of siss; that is, emit is a word with a broader meaning than siss:

Other hypernyms of siss include let loose, let out, utter.

siss (verb)	emit (verb)
make a sharp hissing sound, as if to show disapproval	expel (gases or odors)
express or utter with a hiss	express audibly; utter sounds (not necessarily words)
	give off, send forth, or discharge; as of light, heat, or radiation, vapor, etc.