What do the experts say about it?

Arrogance comes from a lack of self-awareness. The arrogant person cannot see their weaknesses and exaggerate their strengths. Arrogant people tend to not have an accurate picture of how others perceive them and lack an appreciation for the value of others.

Others say this.

 

overbearing pride evidenced by a superior manner toward inferiors
I’ll chime in with my take:  a disgusting quality necessary to cover one’s debilitating self worth.  
I know hundreds of these characters and never found them interesting enough to shine any light on them.  Is that arrogant of me?  But today I fell victim to the lack of awareness of a rather arrogant twenty something.  Oh and they are the worst.  They’ve seen it all in such a short span, but hell are they gifted enough to digest it and manifest it.  Let’s see.  One person is talking, slowly as s/he is thinking while talking.  The arrogant one takes advantage of this gap to jump in and assume the solution or answer exists solely with s/he.  But it turns out that not only do they not have the solution, now someone is tasked with explaining to them why their solution is flawed.  But the arrogant person cannot possibly fathom they’re wrong.  They cast that haughty look like someone walking into a kitchen and smelling cauliflower cooking.  How déclassé. Cauliflower.  And just not the cauliflower itself but anyone who consumes cauliflower.  It’s an inferior vegetable to broccoli.  And the arrogant person thinks to themselves “I have to save these village idiots” until they realize they could care less about wasting their time and intellectual privilege on a subservient person.
What the arrogant person doesn’t understand is just how they’re perceived even though they actually don’t care.  Why should they?  Who are they accountable to?  No one.  No one hovers over their level of status.
So hey you arrogant a-holes, hats off to you.  As much as I dislike the shade you throw, it’s highly entertaining to witness the clueless talk themselves up, especially since 90% of them never hit a college campus, and who’s application of proper grammar rivals a third grader.
You go gurl.  Carry on with your bad ass self cuz we love it.
The whole problem with the world is that fools and fanatics are always so certain of themselves,
and wiser people are so full of doubts.
~ Bertrand Russell