sibilate vs sound out

sibilate and sound out both are verbs.

Word	Noun	Adjective	Verb	Adverb
sibilate	No	No	Yes	No
sound out	No	No	Yes	No

As verbs, sound out is a hypernym of sibilate; that is, sound out is a word with a broader meaning than sibilate:

Other hypernyms of sibilate include articulate, enounce, enunciate, pronounce, say.

sibilate (verb)	sound out (verb)
make a sharp hissing sound, as if to show disapproval	try to learn someone's opinions and intentions
express or utter with a hiss	speak, pronounce, or utter in a certain way
utter a sibilant
pronounce with an initial sibilant