When someone, through some means (usually weight loss), gains a large and sudden boost to their confidence that turns them into egotistical dickheads. It can also exacerbate egos for people who were faking it and now that they have real confidence it makes them appear like they're bragging all the time.
Fella: Hey, did you see that Gary lost a ton of weight recently?
Mate: Yeah! Notice how he hates fat people now? And he scoffs at chicks that he previously would have crawled dick first through a valley of glass just for them to notice him?
Fella: I have!
Mate: Ya boy's got a bad case of Sudden Onset Confidence Syndrome.
When someone uses so much confidence
Her confidenceness is beyond everyone else's
Self-Confidence is what you find within yourself when life tries to make a move at your insecurities. It has been described as the chess Queen piece of human life, killing all the little soldiers other participants send your way. BUT look out, flaunt your self-confidence too much and it might be taken by a bishop. OOPS. Confidence inwards.
"I have the self-confidence of Shrek herself, do not test me"
Playing Confidence man is when a guy willing dates or acts interested in a woman to raise her self esteem
Linda: "Wow I didn't know Rob was into Michelle"
John: "He's not, he's just playing confidence man"
To lose your trouser confidence is when you fart but you are scared it will turn into something wet and far much worse
I had a madrass, 5 pints of guiness and half a dozen whiskeys last night. My trouser confidence is not high
A blowjob from a friend to make your insecurities go away
Bro, you should go get a confidence booster from your friend Anna. You need to love yourself some more.