a frustration boner usually happens when someone is losing at any kind of event, such as a video game. your testosterone is quickly channeled into your penis, causing you to sport a brand new boner fueled by your angry testosterone rush.
after i got stuck with a grenade in halo, i was forced to excuse myself from the game to relieve my frustration boner.
When something is so frustrating, and you cannot possibly grasp it that it gives you a frustrating boner. It could be a math question that you can't wrap your head around, a tag on the back of your boxers that won't stop itching, etc.
Guy1: OH MY FUCKING GOD, the tag on the back of my shirt won't stop itching
Guy2: That's frustrating
Guy1: I have SUCH a frustration boner now