Your question should be: What does 'grrr' mean? And the answer: It means nothing - it's just a low growling sound, like a dog makes. We often use it in informal writing to suggest that the speaker or writer is angry or resentful.

It's the phonetic spelling of an animal's growl. Just what it means depends on the context.

"Grrr" is a slang word. Expressing anger or frustration. It's likely the with the slang word "Argh"