What is the meaning of Tailgate?

A hinged board or hatch at the rear of a vehicle that can be lowered for loading and unloading.

The hinged rear door of a hatchback.

Either of the downstream gates in a canal lock.

Ellipsis of tailgate party.

A tunnel for drawing spent air away from the working face of a mine.

To drive dangerously close behind another vehicle.

To follow another person through access control on their access, rather than on one’s own credentials, especially when entering a door controlled by a card reader.

To privately purchase or sell a security immediately after trading in the same security for a client.

To have a tailgate party.

Source: wiktionary.org