Wiktionary
n. A system of lightbulbs that affix movably to tracks.
Wikipedia
Track lighting is a method of lighting where light fixtures are attached anywhere on a continuous track device which contains electrical conductors. This is as opposed to the routing of electrical wiring to individual light positions. Tracks can be mounted to ceilings or walls, lengthwise down beams, or crosswise across rafters or joists. They can also be hung with rods from especially high places like vaulted ceilings.
Typical systems have line voltage running through a recessed track. The track may have more than one live conductor, so that multiple switched circuits can be used to control different fittings on the same track. This is selected by placing the tab of the connector on the fixture to one side or the other when attaching it to the track. There are three standard types of tracks used in North America, as well as elsewhere in the world. They are often termed "H", "J", and "L" track, after the names of the manufacturers that established the standards, Halo, Juno, and Lightolier. To identify a track fixture, you may use the following two rules: 1. if it has three contacts, it is probably "H" type. 2. If the contact-tips are 1 inch apart, it is probably "J" type, if they are 7/8 inch apart, it is probably "L" type.
Many systems now simply use a single live and then use digital control interfaces such as DALI to control the fittings. This means that each fitting can be independently controlled.
More modern systems are available with low voltage (10, 12, or 24 volts) running through the track, which is in itself decorative. In this case, the fixture may clamp onto a track made of two metal strips separated with an insulating strip. Two-circuit configurations are rare in such systems. The track is powered by a transformer which converts the high voltage into low voltage. There are magnetic and electronic transformers.
Usage examples of "track lighting".
The Couple watched the very handsome boy as he chatted up a thirty-something bartender whose toned muscles were set off by the track lighting over his head.
The walls were grey as well, and track lighting overhead splashed warm light over a row of portraits hung across three walls of the room.
Carpeting, track lighting, a computer terminal, presumably one directly linked to the main computer, and a big screen TV stood against one wall.
Rising from black carpet was a massive black console beneath polished-brass track lighting, with a solid block of brass serving as a table between two black acrylic chairs nearby.
He noticed that a microwave oven had been installed over the conventional one since he'd last been here, and there was now track lighting over the main work areas and the kitchen table, where Bobbi was in the habit of eating most of her meals - usually with a book in her free hand.
She'd drawn the salon's drapes and dimmed the track lighting to create a suitably spectral ambience.
The walls were gray as well, and track lighting overhead splashed warm light over a row of portraits hung across three walls of the room.
Behind it, track lighting with subdued illumination played over the huge glass front of an aquarium.
A pounding headache pierced his temples, stabbing his brain with the artificial track lighting.