What's the term for someone who gives opinions on topics they know nothing about?
And the answer: Ultracrepidarian.
"Ultracrepidarian" is one of those polite words that describe impolite people. The word most likely comes from Latin words meaning "beyond the shoe," and the phrase "the cobbler should not judge beyond his shoe."
The need to describe impolite individuals has existed since antiquity. As the story goes, the famed Greek painter Apelles one day heard a cobbler criticizing the way he had rendered a foot in a painting. While his response has since been lost to time, we might imagine that ultra crepidam, a Latin phrase meaning "beyond the sole," factored into his rebuke.
Today, the phrase can be used to describe someone that attempts to express an opinion about a subject on which they have no knowledge. An example might be:
Ugh! John is being such an ultracrepidarian today. He watched a two-minute YouTube video on dinosaurs and thinks he's an expert!
Other colorful words for annoying or impolite people include a smatchet, a cumber-world, and a flibbertygibbet (no, we're not just making those up). To learn more about definitions of these words and to hear them in a sentence, check out this site.
Congrats! Now that you've finished this article, you won't be an ultracrepidarian about ultracrepidarians.