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.
Gordon's chefs arse crossed the biffins bridge and now he's got sack rot with an infection 'cos he keeps wiping the shit on his nuts. No wonder he's such a mardy bastard!
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