lubricant

Lubricant is an oily or greasy substance that makes machine parts move more easily. If your door squeaks loudly every time you open it, you may want to use some lubricant on its rusty hinges.

When metal surfaces are in contact with each other, especially when they're rough or rusty, there's friction. In order for a machine with moving parts to work quickly and efficiently, it's important to reduce that friction, which is where lubricant comes in. These are usually made mostly of oil, though often they're thicker than a liquid, and they enable two surfaces to slide smoothly against each other, whether that's a key in a lock or engine parts in a car.

Definitions of lubricant
1

n a substance capable of reducing friction by making surfaces smooth or slippery

Synonyms:
lube, lubricating substance, lubricator
Types:
drilling fluid, drilling mud
a mixture of clays and chemicals and water; pumped down the drill pipe to lubricate and cool the drilling bit and to flush out the cuttings and to strengthen the sides of the hole
motor oil
oil used to lubricate the moving parts of a motor
Type of:
substance
a particular kind or species of matter with uniform properties

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