sibilation vs hushing

sibilation and hushing both are nouns.

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

As nouns, sibilation and hushing are synonyms defined as:

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

Other synonyms of sibilation include fizzle, hiss, hissing.

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