hushing vs sibilation

hushing and sibilation both are nouns.

Word	Noun	Adjective	Verb	Adverb
hushing	Yes	No	No	No
sibilation	Yes	No	No	No

As nouns, hushing and sibilation are synonyms defined as:

hushing and sibilation: a fricative sound (especially as an expression of disapproval)

Other synonyms of hushing include fizzle, hiss, hissing.

hushing (noun)	sibilation (noun)
a fricative sound (especially as an expression of disapproval)	pronunciation with a sibilant (hissing or whistling) sound
	a fricative sound (especially as an expression of disapproval)