When your so fucking hungry that you can’t control yourself and you devour your lunch on break time. This is followed by severe disappointment at lunchtime and can lead to lunchtime depression.
Most likely from the French 'luncheon', lunching burst into the American lexicon circa 1992 in the Washington DCMetropolitan Area.
Intransitive verb: to laugh hysterically/uncontrollably
Transitive verb: causing above in another person
Intransitive: "I just saw a fat man driving a tiny car and I started lunching my butt off."
Transitive: "This guy... this guy right here... is lunching me out!"