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Headliner

Part of the automobile-interior overhead or the covering of the roof inside.

Headliner

The fabric lining applied to the inside roof of a vehicle. Also used to describe the fabric lining applied to the inside roof of a truck cap or hard tonneau cover.

Headphones

A key component of an entertainment system, particularly a multichannel entertainment system. Many systems come with wired headphones or with a headphone jack to plug in auxiliary headphones. Some monitors and some portable entertainment systems also include a headphone jack. It is easy to upgrade an existing system to use wireless headphones. See also multichannel headphones.

Headrest Monitor

Part of an entertainment system. This type of monitor is designed to be installed in a vehicle's headrest (or sometimes its seat back). Some headrest monitors include built-in volume and brightness controls on the front, and some include a jack to plug in headphones.

Heads Up Display

Displays images onto the inside of the windshield so the driver can see them without having to take his eyes off the road.

Heads-up

A form of drag racing in which each driver is cued by the Christmas tree to leave the starting line at the same time, and whoever reaches the finish line first wins. As opposed to a bracket race.

Heads-up Display

A display of vital information from a vehicle's gauges that is projected onto the windshield. This might include turn signal indicators, a high-beam indicator, a variety of warning lights (when illuminated) and the speed at which the vehicle is traveling.

Heads-up Display (HUD)

The images of a vehicle's instrument panel, displayed on the inside surface of the windshield in front of the driver where they can seen without taking the eyes off the road.

Heads-up Racer

A race driver that is very good.

Heads-up Racing

Direct, no handicap, competition.

Heat

1. A form of energy released by the burning of fuel. 2. Any temperature above absolute zero.

Heat Dam

The narrow groove cut into the top of the piston. It restricts the flow of heat down into the piston.

Heat Exchanger

An apparatus in which heat is transferred from one medium to another on the principle that heat moves to an object with less heat.

Heat Intensity

The measurement of heat concentration with a thermometer.

Heat Load

The "load" imposed on an air conditioner due to ambient temperature, humidity, and all other factors that produce unwanted heat.

Heat Of Compression

An increase of temperature brought by the compression of gas, air, or an air/fuel mixture.

Heat Of Fusion

The amount of latent heat, in Btu, required to cause a change of state from a solid to a liquid.

Heat Of Respiration

The heat given off by ripening vegetables or fruits in the conversion of starches and sugars.

Heat Quantity

1. The amount of heat as measured on a thermometer. 2. The amount of heat contained in an object measured in Btu's or calories.

Heat Radiation

The transmission of heat from one substance to another while passing through, but not heating, intervening substances.