lubricant, lubricator, lubricating substance

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

• drilling mud, drilling fluid — a mixture of clays and chemicals and water; pumped down the drill pipe to lubricate and cool the drilling bit and to 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

• material, stuff — the tangible substance that goes into the makeup of a physical object