What type of container does Wikipedia name as a way to limit guacamole browning?

Wikipedia names an air-tight container as a way to limit guacamole browning.

The browning is an enzymatic reaction, not simply a sign that the dip has spoiled. Once avocado cells are mashed or cut, polyphenol oxidase can react with oxygen at the exposed surface. That reaction produces brown pigments and is especially noticeable because guacamole has a large surface area in contact with air.

An air-tight container reduces the oxygen available above the guacamole, slowing the reaction. Pressing plastic wrap directly against the surface can provide a similar barrier, because it limits trapped air. Lime or lemon juice may also delay browning by making the mixture more acidic, but citrus does not eliminate the reaction completely.

A common mix-up is the belief that leaving an avocado pit in guacamole prevents browning. The pit protects only the small area it physically covers; sealing the exposed surface is the more relevant principle. Brown guacamole is often still edible if it has been refrigerated and handled safely, although its appearance and sometimes its flavor may be less appealing.