Chasing the dragon
"Chasing the dragon" (CTD) (traditional Chinese: 追龍; simplified Chinese: 追龙; pinyin: zhuī lóng; Jyutping: zeoi1 lung4), or "foily" in Australian English, refers to inhaling the vapor of a powdered psychoactive drug off a heated sheet of aluminum foil. The moving vapor is chased after with a tube (often rolled foil) through which the user inhales. The "chasing" occurs as the user gingerly keeps the liquid moving in order to keep it from overheating and burning up too quickly, on a heat conducting material such as aluminium foil.
Another use of the term "chasing the dragon" refers to the elusive pursuit of a high equal to the user's first in the use of a drug, which after acclimation is no longer achievable. Used in this way, "chasing the dragon" can refer to any recreational drug administered by any means.