Where heavy sweating and chafing on the balls results in itching, burning and in severe cases infection. This is exacerbated by poor hygiene and a hot climate. Similar to trench crack or chefs arse.
Men with sack rot are easily spotted because they look like they just dismounted a horse and adopt a "John Wayne" stance.

A portmanteau of carpe diem, a Latin phrase that means “Seize the Day!” and DM, which stands for Direct Messages. This word means seizing the day via DMs.