v. t. To increase the pressure on (a gas or liquid); as, pressurized oxygen.
Syn. -- supercharge, apply pressure to. [ WordNet 1.5 ]

2. To increase and maintain a pressure in (a compartment or container), above that of the ambient pressure; -- of airplanes, space suits, and diving bells, for example; as, the airplane cabin was pressurized for the comfort of the passengers; the sterile room was pressurized to prevent contamination. [ WordNet 1.5 + PJC ]

negatively pressurized maintained at a pressure somewhat below that of ambient pressure; -- a technique sometimes used to keep airborn materials in a room from escaping out; as, the biohazard lab was negatively pressurized to keep hazardous biological agents from escaping into the environment. [ PJC ]