unwarranted self-importance 

A serious form of narcissism. To act as if one is an important person without actually doing anything worthwhile to prove it, thus making one look like a complete tool.

Sometimes abbreviated as USI.

Idiot: Hey guys! I just put up all these sweet pictures of myself on Facebook, and I've got this vlog that you've gotta check out. If you don't, you're clearly some kind of lesser being, 'cause everyone loves me for no reason!

Smart Person: Sounds like unwarranted self-importance to me.

unwarranted self-importance by IrishBarbarian January 23, 2011

unwarranted piccione 

The act of having an over-inflated sense of one's ability despite no evidence supporting this belief

Gibbo: 'I swear that if I stayed off the piss I could have run the 100m at the Commonwealth Games'

Everyone: 'Gibbo that's unwarranted piccione and you fucking know it'

unwarranted piccione by People's Champ 37 September 26, 2017

Unwarranted Swag

When a person, usually male, walks around carrying more swagger than their body is intended to hold. The most common form of this occurs in sports, when someone constantly surrounds themselves with great athletes and is basically along for the ride to a championship - causing them to believe they were the sole reason their team won.

No one knows why, but great athletes continue to accept the invitation to join his team. The offender of this misdemeanor crime can be easily spotted. His team will be winning, and he will be 5 times slower than the rest of the competition. He will also be the only person talking shit, despite being the worst player on the court/field/etc...

This would be equivalent to Luc Longley talking shit and walking with a limp because Jordan, Pippen, and company won him multiple championships.

This phrase originated in North Central Ohio... but has spread like a wildfire across the country due to the constant desire for losers to be seen as winners.

Andrew: "Is that guy really good? He's walking around like he owns this gym, but he looks like a tool"
Eric: "No, he's got a severe case of unwarranted swag. He was officially diagnosed last year, but is in denial."

Unwarranted Swag by anonymous October 24, 2011

Unwarrantedly 

Adverb.

To act without warrant.

Sheriff Joe Arpaio unwarrantedly believes that all mexicans are dirty, welfare mongering, illegal immigrants.

Unwarrantedly by grammaster August 15, 2012