Children, who presumably wouldn't know a chukker from a chupacabra, reverently handed him polo balls to sign.
From the nytimes.com
Novice fans count on him to let them know that a chukker is a period of play and that there are usually six chukkers in a game.
From the signonsandiego.com
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(polo) one of six divisions into which a polo match is divided
Term used for period of play in polo, seven and a half minutes long, there are six chukkers in a polo match
A seven-and-one-half-minute period in a polo game; from Hindu meaning "a circle."
In technical terms, each game period is known as a chukker. Polo matches can be divided into four, six or eight chukkers, each of which is comprise of seven minutes of actual play time. The clock is stopped every time play is suspended, and after each goal the teams change ends. ...
Also called a period. There a four or six chukkers in a polo game each lasting 7 minutes. A player returns each chukker on a different horse, although a player may rest one for a chukker or two and play the horse again during the game.