Smartypants (noun)

  1. A person who is overly smart, clever, or arrogant.
  2. A person who thinks they are very clever or knows everything.

Origin:

From the phrase "smarty pants".

Examples:

  1. He's such a smartypants, always showing off his knowledge.
  2. She's always correcting people, what a smartypants.
  3. He's always acting like a smartypants and trying to one-up his friends.
  4. The smartypants thought he knew everything.
  5. She's a smartypants who always had a clever comeback.
Some random words: elongate, vitriol, excrescence