siss vs speak

siss and speak both are verbs.

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

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

Other hypernyms of siss include mouth, talk, utter, verbalise, verbalize.

siss (verb)	speak (verb)
make a sharp hissing sound, as if to show disapproval	express in speech
express or utter with a hiss	exchange thoughts; talk with
	use language
	give a speech to
	make a characteristic or natural sound