The act of beating someone or something about the head or head-analog with a large trout or other large fish. Often done in response to them saying something stupid.
"That was the dumbest thing I've ever heard... If I had a fish handy I would have to troutslap you."
This guy could be great but could also be the dumbest guy you ever met. He makes his friends call him trout and is embarrassingly stupid. It is dangerous how stupid this guy is.