Specifically refers to the low, rumbling sound a cat makes when content.
The cat is purring on my lap.
That cat's purring is very loud.
Standard kanji spelling.
Mixed kana-kanji spelling.
Alternate mixed spelling.
Compound of 喉 (のど, 'throat') and 鳴らし (ならし, the noun form of 鳴らす 'to make sound'). Literally 'throat-sounding'.