Bump or Ride-Off:
This occurs when two riders make contact and attempt to push each other off the line of the ball so as to prevent the other from striking the ball. The horses are the ones intended to do the pushing, although a player may use his body as well, but not his elbows. The angle of the bump must be slight so as not to be dangerous to the rider or horse.

Chukka:
There are six chukkas in a polo game, each lasting 7 minutes plus up to 30 seconds in overtime. If during the 30 seconds the ball hits the sideboards or goes out of bounds, or if the empire blows his whistle, the chukka is over. There is no overtime at the end of the sixth chukka unless the score is tied, at which time a seventh period of "sudden death" will be played. A player returns to each chukka on a different pony, although he may rest a pony for a chukka or two and play the same pony again.

Equipment:
The ball is made of plastic or bamboo root it is 3 1/4 inches in diameter and weighs 5 1/2 ounces. The mallets have cane shafts and heads of ash, set at an angle. The length varies from 49 to 54 inches.

Field:
The playing field measures 160 yards wide by 300 yards long. The goals posts which are collapsible on impact are spaced 24 feet apart and are 10 feet high.

Goal:
Any time the ball crosses the line between the goal posts is considered a goal regardless of whether a horse or a mallet caused the ball to go through. The teams change sides after every goal is scored.

Handicap:
All registered players are rated on a scale of -2 to 10 - the higher the better. Although the word "goal" is often used after the digit, it bears no relation to the number of goals a player might score, only to his ability. The handicap of the team is the sum total rating of each player and in handicap matches the team with the higher handicap gives the difference in rating to the other team. For example, a 6 goal team will give two goals to a 4 goal team.

Hook:
A player may spoil another's shot by putting his mallet in the way of the striking player's mallet. A cross hook occurs when the player reaches over his opponent's mount in an attempt to hook; this is considered a foul.

Knock-In:
Should a team, in an offensive drive, hit the ball across the opponent's endline, the defending team resumes the game with a free hit from their endline. No time out is allowed for knock-ins.

Nearside:
The left hand side of a horse.

Offside:
The right hand side of a horse.

Neckshot:
A ball which is hit under the horse's neck from either side.

Tail Shot:
Hitting the ball behind and across the horse's rump.

Out Of Bounds:
When a ball crosses the sideline or goes over the sideboards, it is considered out of bounds and the umpire throws in another ball between the two teams at that point. No time out is allowed for an out-of-bounds ball.

Penalties:
A free hit towards the goal from a set distance. The severity of the foul committed determines what penalty will be awarded - the range is as follows:

1. An automatic goal
2. A free hit from 30 yards to an undefended goal
3. A free fit from 40 yards to an undefended goal
4. A free hit from 60 yards to a defended goal
5. A safety. This occurs when a ball is hit, or deflected behind the back line by a player of the defending team. The penalty for a safety is a free hit by the offensive team, 60 yards from the goal, at a point in line where the ball crossed the back line.

Polo Pony:
The polo pony is selected for his ability to carry weight at great speed, and for his endurance. There is no height limit, although most are between 15 and 15.3 hands and the age is generally between 5 and 15 years. A pony's training must make him agile and responsive to every command and impulse of the rider. He becomes so familiar with the various shots and manoeuvres that he can often anticipate his rider's wishes. Action of horse and rider alike must be instantaneous to be effective, thus the pony becomes a player in the game.

Start:
The four players of each team line up in the middle of the field, facing the side boards. The umpire rides toward them, throws the ball between them, and the game play begins. Play is resumed in the same way after each goal, with teams changing goals.

Teams:
Four players constitute a team. The No. 1 and No. 2 players are primarily offensive players and advance the ball to the goal. No. 3 is a roving player, and usually the best player on the team. It is his responsibility to be prepared to pass the ball forward, attack the goal himself, or drop back to aid in the defence. The No. 4 or "Back" as he is referred to is basically responsible for defence, although he may turn a play into an attacking situation much the same as Number 3.

Throw-In:
A chukka begins and many plays resume with the umpire bowling the ball between the two ready teams.

Time Out:
An umpire calls time out when a foul is committed, an accident occurs, or at his own discretion. A player may only call time out if he has broken tack or is injured. No time out is allowed for changing horses or replacing a broken mallet, although a player may do so at any time.

Umpire:
Two mounted umpires (one for each side of the field) consult each other after each infringement and impose a penalty only if they agree. If they do not agree they ride to the sidelines to confer with the third man.

Third Man:
The referee sitting at the sidelines. If and when the umpires on the field are in disagreement, the third man makes the final decision.