Rugby is defined by Merriam-Webster as "a football game in which play is continuous without time-outs or substitutions, interference and forward passing are not permitted, and kicking, dribbling, lateral passing, and tackling are featured."
The sport was originally developed as a variation on traditional English football (or soccer) in the 19th century, with the main innovation being that players were permitted to run with the ball and tackle.
As opposed to a soccer ball, which is round, the rugby ball is larger and oval-shaped, similar to an oversized football, rounded at the edges.
Points in rugby can be scored in several ways. A try, worth five points, is scored by touching the ball down in the opponent's goal area; a conversion, worth two points, is scored by kicking the ball through the goalposts after a successful try; a goal kick, worth three points, is scored by kicking the ball through the goal posts during a penalty kick or during play.
Play is restarted after an infraction with a formation called the scrum, in which eight players from each side interlock bodies and struggle for possession, or hooking, of the ball.
There are also several different variations on rugby (rugby union, rugby league, rugby sevens), involving the number of players on each side.
For a more in-depth guide to rugby, including explanations of the line-out, the ruck and the maul, go to news.bbc.co.uk/sport2/hi/rugby_union/rules_and_equipment. And to learn more about Rocky Gorge Rugby, go to pitchero.com/clubs/rockygorge.