1. Someone who acts as an expert but clearly isn't.
2. Knowingly guessing at a response but speaking with conviction. A
combination of Faux (fake) and SME (subject-matter-expert) (
Pronunciation: \ˈfō-smē\). It can be used as an
adjective or a verb.
You: "I wonder how long it took to build this
roller coaster?"
Fauxsme: "I bet it took 40 guys at least 3 months to
finish this off."
You: "Don't be a fauxsme, you clearly have no idea whatsoever."
Or
If I had to fauxsme this one, I'd bet it took 40 guys at least 4 months to
finish this off.