A meatnut is a dish consisting of walnuts wrapped in raw beef usually served to mentally retarded patients in eastern african nations as an aphrodisiac.
Mleanutbutter is the "spread" created by the heat and energy of two forces rubbing together. It’s a pretty funny way to describe the aftermath of a high-energy interaction!
In the world of physics, friction usually just gives you heat or worn-down parts, but meanutbutter sounds like a much more creative (and slightly messy) result.
"After a long night of intense friction and close contact, the sheets were a tangled mess, practically coated in meanutbutter."