Tailgating

Tailgating has a number of different meanings, loosely based on the tailgate present on many vehicles such as light trucks and station wagons:

The practice of driving closely (less than one vehicle-length per 10 mph) behind another vehicle on a roadway, it is a form of intimidation as the tailgating driver is effectively threatening to damage the victim vehicle and its occupants by crashing into it if the victim driver does not do something (often illegal, like increasing his/her speed beyond the speed limit) to placate the tailgater. Tailgating is thus a particularly virulent form of road rage.

Derived further from this are:-

The practice of following someone with a security code or keycard through a security door, generally in workplaces.

In finance, tailgating means the action of a broker or advisor purchasing or selling a security for his or her client(s) and then immediately making the same transaction in his or her own account. This is not illegal like front running, but it is not looked upon favorably because the broker is most likely placing a trade for his or her own account based on what the client knows (like inside information).

In North America, tailgating can refer to the (often celebratory) practice of eating and socializing while perched on the open tailgate of a vehicle (though many people participate even if their vehicles don't have tailgates). This may include barbecueing and is usually related to sports fans preparing for Canadian football, ice hockey, or American football games. These events are also known as tailgate parties.