To pressurize something means to increase the air pressure inside it, making the air molecules pack more tightly together than they would naturally. Airplanes flying at high altitudes pressurize their cabins because the air outside is too thin to breathe comfortably. The plane's systems pump air into the cabin and seal it tight, creating an artificial environment where passengers can breathe normally even though they're 35,000 feet above the ground.

You experience pressure differences when your ears pop during takeoff or landing: that's your body adjusting to the changing air pressure. Scuba tanks work the same way, storing pressurized air so divers can breathe underwater. A pressure cooker pressurizes steam to cook food faster than normal boiling.

The word can also mean to put strong pressure on someone to do something. A coach might pressurize players to perform better, or a salesperson might pressurize customers into buying something quickly. In this sense, it's similar to pressure as a verb, meaning to push someone hard toward a decision or action.