Overflowing, typically in a non-literal, metaphorical sense. Origins lie in the inability to use real words at important occasions often experienced by artists and philosophers.
"I'm cheffing with relief that I am not you," he said.
To cook food on a higher level than a quick simple meal, as if one is a chef.
I always cook for my girlfriend, but I am cheffing for her this time. Everything will be made from scratch. It will take longer, but nothing will be prepackaged.