Arising from a wasted slurring of the two wonderful words "rug muncher", a runcher is someone who devours something with the voracity of a lesbian on heat piling mouth first into pussy.
Related to the mysterious and as yet undefined "duncher"...
"Yo, you are a such a fucking runcher!"
"He runched that down"
"Im so goddamn runchy today!"
The Best Fifa youtuber in all of youtube history, much better than the egg which is bateson 87, better fut market controller than nick rtfm and better content than castro, better rages than that Norwegian kid