Top definition
When a man gets sexually aroused and 'horny' so he masturbates and when he cums he lets his seaman fly into the fish tank, killing the fish, but resolving his sexual fustration.
I had a wank last night and didn't want a huge mess all over the carpet so I did it in the fish tank!

Shit, i appear to have killed my fish.

Fish-Tank Wank's are the best!
by Helen Back April 16, 2007
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