whirr vs purr

whirr and purr both are nouns.

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

As verbs, whirr and purr are synonyms defined as:

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

whirr (noun)	purr (noun)
sound of something in rapid motion	a low vibrating sound typical of a contented cat

whirr (verb)	purr (verb)
make a vibrant sound, as of some birds	indicate pleasure by purring; characteristic of cats
make a soft swishing sound	make a soft swishing sound