To consume large amounts of over the counter cough syrup. Most Specifically Robotussin Cough and Cold Maxium Strength. It is named after the main active ingrediant (Dextromethorphan Hydrobromide) which makes you "Trip Balls". To be Dexed it is recommended to consume between 700-1600 mg otherwise your just a pussy.
Me and Sally were dexing behind the gym, she bought DM brand and we threw up all day in class