Having or soon to have a massive boner, woodie or hard-on so large you will brutally erupt all over yourself. CAUTION: the act of a trouser explosion may impose to scrotem bursting, trouser leakage and major skin sack reduction.
Guy 1: Did you have fun last night with ur girl?
Guy 2: Yea but i had a major trouser explosion.
Guy 1:What happened?
Guy 2:She grabbed my wang.
Guy 2 :Yea except for one thing my cock popped.
Guy 2:Plus it was ur sister and she drowned in semen