Cocksure

[Tina]

A condition of extreme (sometimes foolish) confidence or boldness pertainng to or having to do with the size of ones penis ([cock])

[Dianne]

premature assumption of the complete and utter truth in ones thoughts, opinions, and actions. Cocking your gun with no ammo. Gunning your cock at anything that moves.

[Julene]

A feeling of confidence, superiority, greatness, and swagger only obtained by pure animals. This attitude or lifestyle in fact has absolutely nothing to do with the size of ones penis, but is more a way of life for wildmen.

[Cami]

to be very very sure, so sure that youd bet you cock on it. From the classic British novel, Heart of Gayness

[Dave Paprocki]

To be incredibly boastful over the size of your penis; being excessively overconfident about the size of ones cock.

[Sommer]

To be outlandishly boastful over the size of your penis; excessively overconfident about the size of ones cock.

[Rihanna]

[overly confident] and [arrogant] a feeling of [superiority] over everything

[Donald Trump]

Presumptuously or arrogantly confident.

[exinilu]

too confident, in a way that is slightly unpleasant or rude: