Definition from Wiktionary, the free dictionary
ultracrepidarian (plural ultracrepidarians)
- Of a critic, giving opinions on something beyond his or her knowledge.
- "[Inspector Queen] was the only person in New York who might be called, without intent to malign, an Ultracrepidarian critic. It was of the very nature of his job to find fault with small and insignificant details." -- The American Gun Mystery by Ellery Queen
criticizing things beyond one's knowledge