When you're jacking off and an unexpected unexciting event comes by. Like a family member calling you, or your phone ringing, your boss or co-worker asking you WTF you are doing so long in the toilets. An erection bomber will ruin your erection, and therefore, your entire session.
-WHAT THE HELL are you doing in the toilets? It's been almost a half an hour dammit!
-F*CK YOU Bernard! You're such a fucking erection bomber!
- Well, it's not Bernard actually... And for the record, you're suspended asshole!