This word was very popular in and around the Washington DC area. I first heard the word circa 1985 in high school. Veriable definition. Could be crazy, high, insane, tripping, pissed or thousands of other meaning. Definition is dependent upon the context. Example

A euphemism for “kill me” now that composting oneself after one’s death has become popular.

D.C. Metro area term for being absurd, ridiculous, or idiotic.

i.e. out to lunch

Lunching - Gerund: Washington D.C. term meaning that someone is acting stupid or lame. Similar to "out to lunch". Also, "lunchin'" or noun, "lunch box"

a D.C word that can encompass any act when presented in the proper context.

The art of everything lunching. Can be used in any shape or form. The word really has no definition because the people who utilize it (usually potheads residing in the Washington D.C./ Montgomery County Area) only do so as a variable. Everything can be lunching, and at the same time nothing can be lunching. The word is not something to be learned; rather, it is a word to be understood, and once understood, can, and most probably will become a word you use in your vocabulary more often than linking operaters like "the" or "and".

Origins: The origin of the word and it's definition is very different from what it has become today. Supposedly, in a high school in Rockville, Maryland, there was a very obese student who used to sit all by himself in the Cafeteria and eat his lunch, which consisted of anything and everything that could be eaten. Fellow classmates called this boy a "Lunchbox" see "Lunchbox" for detailed defitinition. The word evolved from there.

to act weird do crazy stuff act stupid