Not to be confused with a one hit wonder
(a music act that only had one song ever make it), a one-hitter is a small, easily-concealed device for smoking marijuana
ly. A large assortment of tiny, folding, and/or collapsible
pipes are available, and some even have mechanism
s like lids to protect the burning material for easy and rapid stowage.
There is a popular type of one-hitter that is eminently suitable to smoking pot in public. The reason it is suitable is because it looks like a cigarette, from the white shaft to the brown filter. In actuality, the look is paint, and the "cigarette" is a horizontally-oriented pipe with a small bowl at the end large enough for one hit.
The pipe usually comes with a slim wooden box with two compartments, one for the pipe, and one for the pot. A wooden door fits snugly into the top, blocking odors (from people only) and enabling you to easily carry it about in your pocket. (One can buy them at almost every tobacco/convenience store in a major city (or in the seedier sections of small cities) for about $25, wooden box and all.)
In use, one takes the "cigarette" and jams the pipe end into the hollow in the box with the pot, compressing a small amount into the end. (With practice, it looks like you're simply tapping your smoke to pack it prior to lighting.) One then simply lights, holds, and smokes it as if it were a cigarette with nobody the wiser.
In my experience I've heard that even if people nearby smell it, they won't suspect the person obviously smoking a cigarette several yards away.