1. A deliberate misspelling of the word “dumb,” meaning worse than stupid; intentional idiocy.
2. Any deliberate, spectacularly miserable failure masked as “mission accomplished.” From the presidential nickname, “Dubya” and “dumb.”
Nick- Uh, Larnie, "D-U-B-M" spells "dubbum."
Larnie- (thinking) ...I hate you.
Nick- Sorry, gotta go, I hear your wife calling! Be sure to write when you learn how! Hey, guess what everybody, Larnie says I'm dubm!