Beeing lazy and watch tv or read and just do as little as possible when you could do other stuff. The reason for the term is that the catfish generally hang out on the bottom of the water, being lazy and doing all they need there without moving unnecessarily.
"I'm really tired, you up for some catfishing?"
"We could do some trekking, but I would prefer to take a chill day and just catfish."
"Catfishing sounds good to me."