The act of putting a fish in a girls vagina, then fishing it out with your teeth. Also a masturbating technique for girls, except they use their fingers instead of teeth.
Guy 1 "My girlfriend got a goldfish the other day."
Guy 2 "Why? Those things are boring as hell, man."
Guy 1 "Yeah she thought so too. She just wanted one handy in case she wanted to dunderfish"
Guy 2 "Oh that's smart thinking."