hushing vs hissing

hushing and hissing both are nouns.

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

As nouns, hushing and hissing are synonyms defined as:

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

Other synonyms of hushing include fizzle, hiss, sibilation.

hushing (noun)	hissing (noun)
a fricative sound (especially as an expression of disapproval)	a fricative sound (especially as an expression of disapproval)