Toothing, or bluetoothing, is the practice of using Bluetooth-enabled mobile devices to find partners for anonymous casual sex. Technology magazines, such as Wired, have written about this phenomenon that is sweeping commuter trains coming into London.

Bluetooth-enabled devices are capable of finding other Bluetooth-enabled devices in their physical vicinity. Once contact has been established with another Bluetooth device, users can communicate using conventional means, such as SMS messages (known casually in Britain as "texting").

Owners of Bluetooth-enabled devices send text messages requesting sex to others like them when they're temporarily in close proximity, such as in a commuter train. SMS requests for anonymous sex usually begin with the simple message "'Toothing?". The brief period of courtship consists of the exchange of text messages teasing either or both people involved to locate each other in the train. The casual encounters are finally consummated in the loo. As quoted in Wired, one gentleman who recently engaged in toothing thinks that "it sure beats doing the crossword!"