Past-tense of the word lunch. See that definition for a good idea of what lunched is. It means to do something stupid, or to mess something up. It originated from the
stoner-culture, and used to be associated with being
high or burnt. But that is not always the case anymore.
Go read the definition for lunch if you still don't understand.
You also hear, "lunched out". Same thing, just a different way to say it.
Definitely regional, I've only heard the word used in
DC when I lived there, and we said it ALL the
time! Since moving from there, no one I've met has ever heard of it.
Awww, man, I lunched! I drove all the
way here and forgot the dang receipt!
After all that planning, he lunched out and walked through the security gate with a
nug stuck to his fleece! Needless to say, he got arrested, what an idiot!