A cartoon of a lit cigarette with smoke. Often used in its direct meaning. The emoji refers to a tobacco cigarette, in general, but could also represent other smoking substances: cannabis (marijuana); vape; herbal cigarette, etc.
This symbol was was originally created as a "SMOKING SIGN" that indicates a smoking room or other areas, where smoking is allowed. There is also the 🚭No Smoking emoji, which has diametrically opposite in meaning, and looks like the 🚫 Prohibited emoji over a cigarette.