Wiktionary
n. (context games English) A game, played upon a table which lightly spurts air out of various holes on its surface in order to reduce friction, where each player must hit a light flat plastic puck into their opponent's goal using their own plastic mallet.
Wikipedia
Air hockey is a game where 2 players play against each other on a low-friction table. Air hockey requires an air-hockey table, two player-held paddles, and a puck.
A typical air hockey table consists of large smooth playing surface, a surrounding rail to prevent the puck and paddles from leaving the table, and slots in the rail at either end of the table that serve as goals. On the ends of the table behind and below the goals, there is usually a puck return. Additionally, tables will typically have some sort of machinery that produces a cushion of air on the play surface through tiny holes, with the purpose of reducing friction and increasing play speed. In some tables, the machinery is eschewed in favor of a slick table surface, usually plastic, in the interest of saving money in both manufacturing and maintenance costs. Note that these tables are technically not air hockey tables since no air is involved, however, they are still generally understood to be as such due to the basic similarity of gameplay. There also exist pucks that use a battery and fan to generate their own air cushion, but as they are prone to breakage, they are commonly marketed only as toys. An air hockey table has very little friction.
The only tables that are approved for play and sanctioned by the USAA (United States Air Hockey Association) for tournament play are 8-foot tables. Approved tables include all Gold Standard Games 8-foot tables; some 8-foot tables from Dynamo; and the original 8-foot commercial Brunswick tables. Other full-size novelty-type tables with flashing lights on the field of play, painted rails, and/or smaller pucks are not approved for tournament play but can be used to learn the game. For an updated list of sanctioned tables, consult the USAA rules at goldstandardairhockey.com, airhockey.com, or airhockeyworld.com.
A paddle (sometimes called a goalie, striker or mallet ) consists of a simple handle attached to a flat surface that will usually lie flush with the surface of the table. The most common paddles, called "high-tops", resemble small plastic sombreros, but other paddles, "flat-tops", are used with a shorter nub.
Air Hockey pucks are discs made of Lexan polycarbonate resin. Standard USAA-approved pucks are yellow, red, and green. In competitive play, a layer of thin white tape is placed on the face-up side. Air Hockey pucks come in circles and other shapes (triangle, hexagon, octagon, or square).
Four-player tables also exist, but they are not sanctioned for competitive play.