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1.
When a person masturbates in a concealed area like an alley, then rushes out to ejaculate on an unsuspecting passerby.

It can be done from a ceiling, a window, or the street. So long as it involves someone unexpectedly getting spermed on, it's sperm sharking.
Guy 1: Melody told me she was sitting in the park the other day, when this homeless guy came out of nowhere and jizzed on her clothes.
Guy 2: Jesus Christ!
Guy 1: Apparently it's called Sperm Sharking.
Guy 2: Why is that?
Guy 1: Cause of the whole unexpected Jaws thing. Du-dun du-dun...
by YouTubeWatcher March 24, 2009
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