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When a male becomes aroused while showering. It can be either devastatingly inconvenient or curiously enjoyable. It is usually caused by overly frisky scrubbing or simply unclean shower thoughts.
Man 1: "Sorry that took so long, man. I got an unexpected showerection."

Man 2: "Dude you were in there for an hour and a half."
by themilkmantrink July 16, 2011