An idiom to describe someone who thinks he/she is wiser than others

Question

Is there an idiom in English to describe someone who thinks he/she is smarter/wiser than everyone else?

In Polish, we have an idiom, which literally translated, would sound like:

He/she has eaten all minds

Answer 1

In English, a common term for such a person is "know-it-all", as in:

Ever since Bob took that first-year philosophy course, he's acting like such a know-it-all.

Usually the phrase has a slightly negative connotation to it, because it implies that the person really doesn't know it all, but they might act arrogant as if they do know it all.

Answer 2

There are numerous amusing English terms for such a person, including
• wiseacre (“One who feigns knowledge or cleverness; an insolent upstart”),
• smarty-pants (“A smart aleck or know-it-all”),
• clever dick (“(chiefly UK) A person who annoyingly tries too hard to impress with their cleverness”),
• smart aleck (“One who is pretentious about their own cleverness or knowledge; a know-it-all”, but also with senses “One who is obnoxiously self-assured; a show off” and “One who is given to obnoxious or insolent humor; a wise guy”).

Some terms related to the above, but with slightly different meanings, include
• wiseass (“One who makes wisecracks, particularly in a sassy or cocky fashion”),
• smartass (“(slang) One who is particularly insolent, who tends to make snide remarks or jokes”).

Answer 3

Though "know-it-all" is my #1 go-to phrase for that meaning, another expression with a smart-alecky negative connotation would be to refer to someone as "Einstein", as in:

"Einstein, here, has all the answers!"

Of course, the reference would be to Albert Einstein, the theoretical physicist:

Answer 4

How about: "He[she] is full of himself[herself]"? That's a pretty common English idiom.

Answer 5

Charlatan is the word to describe such person