A grease gun is a hand-operated, pneumatic, or battery-powered tool used to apply lubricant (grease) to moving mechanical parts such as bearings, joints, gears, and machine fittings. It consists of a cylindrical barrel (cartridge holder), a plunger or pumping mechanism, a handle or trigger, and a flexible hose with a nozzle (coupler) that fits onto grease fittings (nipple points). It is commonly used in automotive maintenance, construction machinery, and industrial equipment servicing to reduce friction and wear.

Operation
To operate a grease gun, the grease cartridge is inserted into the barrel, or the gun is filled with bulk grease. The nozzle is then attached to the grease fitting on the machine part. When the handle is pumped or the trigger is pressed, pressure is created inside the barrel, forcing grease through the hose and out of the nozzle. The grease is injected into the fitting and spreads inside the moving parts, providing lubrication and reducing friction. The operator continues pumping until the required amount of grease is applied, then removes the nozzle carefully to avoid leakage.