A bong (also water pipe, billy, bing, or moof) is a filtration device generally used for smoking cannabis, tobacco, or other herbal substances.
In construction and function a bong is similar to a hookah, except smaller and especially more portable. A bong may be constructed from any air- and water-tight vessel by adding a bowl and stem apparatus (or slide) which guides air downward to below water level whence it bubbles upward ("bubbler") during use. To get fresh air into the bong and harvest the last remaining smoke, a hole known as the "carburator", "carb", "choke", "bink", "rush", "shotty", "kick hole", or simply "hole", somewhere on the lower part of the bong above water level, is first kept covered during the smoking process, then opened to allow the smoke to be drawn into the respiratory system.
The word bong is an adaptation of the Thai word bong or baung (Thai: บ้อง, [bɔ̂ŋ]), which refers to a cylindrical wooden tube, pipe, or container cut from bamboo, and which also refers to the bong used for smoking.