whir vs whirr

whir and whirr both are nouns.

Word	Noun	Adjective	Verb	Adverb
whir	Yes	No	Yes	No
whirr	Yes	No	Yes	No

As nouns, whir and whirr are synonyms defined as:

Other synonyms of whir include birr, whirring.

As verbs, whir and whirr are synonyms defined as:

Other synonyms of whir include birr, purr, whiz, whizz.

whir (noun)	whirr (noun)
sound of something in rapid motion	sound of something in rapid motion

whir (verb)	whirr (verb)
make a soft swishing sound	make a vibrant sound, as of some birds
	make a soft swishing sound