A swollen and irritated anus caused by any number of maladies, including anal sex, greasy bowel movements, or dirty thongs. Also used metaphorically to imply being beaten down my life's injustices, as in "my boss is such a dick. I need a drink cuz the work week left my corn chapped and swollen."
There's no fucking way I can go dancing tonight. My chapped corn is rawer than a shaved clitoris.