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.

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.