Tailgate is an American English

American English

American English is a set of dialects of the English language used mostly in the United States. Approximately two-thirds of the world's native speakers of English live in the United States....

 word denoting the door or 'gate' at the back of a wagon

Station wagon

A station wagon is a body style variant of a sedan/saloon with its roof extended rearward over a shared passenger/cargo volume with access at the back via a third or fifth door , instead of a trunk lid...

, pickup truck

Pickup truck

A pickup truck is a light motor vehicle with an open-top rear cargo area .-Definition:...

, SUV or other similar type of vehicle

Vehicle

A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....

 that is hinged at the bottom and can be opened for the convenience in loading cargo into the rear of the vehicle. A similar vehicular feature, the hatch

Hatch

Hatch may refer to:* Hatching, also called "cross-hatching", an artistic technique used to create tonal or shading effects using closely spaced parallel lines* Hatching, the emergence of a young animal from an egg...

, hatchback

Hatchback

A Hatchback is a car body style incorporating a shared passenger and cargo volume, with rearmost accessibility via a rear third or fifth door, typically a top-hinged liftgate—and features such as fold-down rear seats to enable flexibility within the shared passenger/cargo volume. As a two-box...

 or liftgate

Liftgate

A liftgate, also called a hatch, hatchback or liftback, is a closure at the rear of a vehicle that can be mechanically raised during loading and unloading of cargo...

, is a door at the back of a vehicle that is hinged at the top and opens upward. In modern usage, the word tailgate may refer to a true tailgate, a hatchback or a lateral opening door (hinged on the left or right side) in the back of a pickup truck, wagon or SUV.

In British English

British English

British English, or English , is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere...

, the tailgate is commonly referred to as the 'boot' and sometimes called the hatch, is a door

Door

A door is a movable structure used to open and close off an entrance, typically consisting of a panel that swings on hinges or that slides or rotates inside of a space....

 on the back of a vehicle that can be moved either up or down, such as on a pickup truck

Pickup truck

A pickup truck is a light motor vehicle with an open-top rear cargo area .-Definition:...

 or hatchback

Hatchback

A Hatchback is a car body style incorporating a shared passenger and cargo volume, with rearmost accessibility via a rear third or fifth door, typically a top-hinged liftgate—and features such as fold-down rear seats to enable flexibility within the shared passenger/cargo volume. As a two-box...

.

Tailgates can also be furnished with additional accessories like a "Pocket" for storage purposes etc.

The following terms were derived from the noun tailgate:

• Driving closely behind another vehicle
  The verb to tailgate
  Tailgating
  Tailgating is the practice of driving on a road too close to the vehicle in front, at a distance which does not guarantee that stopping to avoid collision is possible...
  
  refers to the practice of driving closely behind the rear fender of a preceding vehicle.
• Entering an area without authorization verification
  The term also refers to closely following someone, such as through a door or gate, where individual passes may be required, also known as "piggybacking
  Piggybacking (security)
  In security, piggybacking refers to when a person tags along with another person who is authorized to gain entry into a restricted area, or pass a certain checkpoint. The act may be legal or illegal, authorized or unauthorized, depending on the circumstances...
  
  ".
• Tailgate party
  The term tailgate party
  Tailgate party
  In the United States, a tailgate party is a social event held on and around the open tailgate of a vehicle. Tailgating often involves consuming alcoholic beverages and grilling food. Tailgate parties usually occur in the parking lots at stadiums and arenas, before and occasionally after games and...
  
  refers to the practice of engaging in a social drinking and/or eating event that is based out of the back of one's truck, wagon or SUV.