A pick up game is a game of some kind that is not part of a regularly scheduled season of competition or a championship series. Instead, it is a more-or-less spontaneous game, with teams often made up on the spot. There are no repercussions beyond the final score in terms of standings or future commitment.
There are a number of ways that pick up games come about. One way depends on numbers — either the minimum needed to make the game work or the regulation number. In this method, people hang around until enough players show up and are willing to stay for the duration of a game.
Another way pick up games come about involves a semi-regular meeting, to which many are invited but no one is committed to show up. This is the case when, for example, there's a basketball night every Monday at a local school gym. Many more people than come on any particular Monday may know about the game, but they come as their schedule permits. Whoever shows up, plays, and if that means unequal numbers on the teams, players usually try to make it as fair as possible by considering talent, height, or other relevant factors for the situation.
Recently, attempts have been made to use the Internet to schedule pick up games. This is a way of helping people connect with other players in their local area and allows aficionados to have complete teams whenever possible. Potential players are asked to provide their gender, game choice, age, location, and how far they are willing to travel to a game.
Basketball used to be the sport usually meant when the term pick up game was used, but the types of competitions that use the designation pick up game has expanded. It is now used to refer to casually scheduled or show-up-and-play games of softball, volleyball, tennis, dodgeball, and even chess.
Pick up games are spontaneous and not between pre-set teams, so they resort to a variety of methods for picking teams and identifying them. Captains may be elected to pick teams, or players may be counted off with the Ones playing the Twos. An all-men's sports pick up game may be played as Shirts versus No Shirts as an easy way to be able to identify teammates and distinguish them from the opponents. Shirts versus Inside-Out Shirts, White Shirts versus Colored Shirts, and Men versus Women are other team definitions created with the goal of knowing who is who. In chess, it's simple: one player just sits down on one side of the board or the other.