What does "know-it-all" mean?

Someone who claims to be knowledgeable or an expert in something, obnoxiously dismissing the opinions, advice, suggestions, etc. of others.

How do you pronounce "know-it-all"?

Pronounced //ˈnəʉ.ɪt.oːl//.

Common synonyms include: know-all, aggressively self-confident, biggety, braggart, buddha, bumptious.

//ˈnəʉ.ɪt.oːl// noun

noun ·Uncommon ·Advanced level

Noun

1
Someone who claims to be knowledgeable or an expert in something, obnoxiously dismissing the opinions, advice, suggestions, etc. of others. US, derogatory
"We had it all figured out, but this know-it-all marched in with "the correct way of solving it", leaving our experiment in shambles."
2
someone who thinks they know everything and refuses to accept advice or information from others wordnet