Learning Arimaa/Glossary

Arimaa Challenge
Until the year 2020, the first person or organization who develops a computer program that can defeat three top human players will receive a cash prize.

Blockade
A piece that is not frozen, and yet still unable to move is blockaded. This occurs when it is surrounded by pieces that it cannot push out of the way. See also Immobilization, Frame.

Camel
The second strongest of the six unique Arimaa pieces.

Capture
See  Trap (verb).

Cat
The fifth strongest of the six unique Arimaa pieces.

Dog
The fourth strongest of the six unique Arimaa pieces.

East Wing
The right side of the board viewed from Gold's perspective, specifically the f-, g-, and h-files.

Elephant
The strongest of the six unique Arimaa pieces. The Elephant is the only piece that cannot be pushed or pulled by the enemy.

Elimination
A player wins the game by elimination if the opposing player has no Rabbits left.

Exchange
Occurs when each side traps a piece of equal strength, usually within a short period of time. For example, if each side captured a Rabbit on consecutive moves it is described as a Rabbit Exchange. See also  Trap (verb).

False Protection
When two pieces adjacent to a trap appear to be mutually protected, but in fact, both are in danger of being trapped due to strong enemy pieces adjacent to them. See also  Mutual Protection.

Fence
When an opponent's piece is frozen and partially  blockaded such that if unfrozen the only  step it could take is into an unprotected  trap.

File
One of eight columns on an Arimaa board. From Gold's perspective, the a-file is on the left and the h-file is on the right. It is the opposite from Silver's perspective.

Flip
The combination of pulling and  pushing an opponent's weaker pieces such that the weaker piece appears to be flipped to the other side of the stronger piece. Weaker pieces are vulnerable to being flipped to the opponent's side and eventually being trapped. See also  Swing and  Throw.

Fork
A fork occurs if a piece is simultaneously threatened with capture in two different traps. This can only occur on the squares c4, c5, d3, d6, e3, e6, f4 and f5.

Frame
A piece which is on a trap square, surrounded on three sides by opposing pieces which prevent it from pushing its way off the trap square, has been framed. See also  Pin and  Trap (noun).

Freeze
A piece is frozen if it is adjacent to a stronger enemy piece and is not adjacent to any friendly pieces. A frozen piece cannot move until the enemy piece moves away or a friendly piece moves onto an adjacent square.

Goal
A player wins the game by goal if one of his/her Rabbits advances to the opponent's home rank.

Gold
The player with the Gold pieces is both the first to setup and the first to move. See also  Silver.

Home Trap
A trap on a player's third rank. The squares c3 and f3 are Gold's home traps; the squares c6 and f6 are  Silver's home traps,

Horse
The third strongest of the six unique Arimaa pieces.

Hostage
A piece that is frozen 2 squares away from a  trap square is a hostage. If the trap is undefended, and the hostage-holder is mobile, the hostage piece can be trapped in one move.

Immobilization
A player wins the game by immobilization if the opposing player has no pieces remaining or is unable to make a single legal move. See also Blockade

Invade
When a player uses two to more pieces to take control of an opponent's home trap. The pieces near that trap usually scatter. See also  Scatter.

Move
See  Turn.

Mutual Protection
When two or more pieces adjacent to a trap prevent each other from being  trapped by stronger enemy pieces. See also  False Protection.

Overload
A major piece (usually an Elephant) is said to be overloaded if it must simultaneously protect multiple friendly pieces at two different  traps.

Overwhelm
A major piece (usually an Elephant) is said to be overwhelmed if a group of weaker enemy pieces work together such that it is not able to  trap any of them.

Pin
A lone friendly piece that is supporting a framed piece is said to be pinned. See also  Frame.

Postal Game
A slow game in which the players are allowed a specified number of days (sometimes hours) to complete each move. Historically postal games (e.g. chess, go) were played by old-fashioned mail and a single game could last for years. Nowadays, postal games are normally played online in a period of weeks or months. Also known as a correspondence game.

Pull
A player can pull an enemy piece with a stronger piece by first moving the friendly piece to one of the unoccupied adjacent squares and then moving the opponent's piece into the square that was just vacated. A pull requires 2 steps. See also  Step.

Push
A player can push an enemy piece with a stronger friendly piece by first moving the opponent's piece to one of the adjacent squares and then replacing it with the friendly piece. A push requires 2 steps. See also  Step.

Quadrant
A quarter of the board (16 squares), usually distinguished either by the trap square it contains, or by compass directions from the perspective of  Gold. Thus the c6-quadrant is also the northwest quadrant, etc.

Rabbit
The weakest unit on the board and the only piece that cannot move backwards. However, Rabbits are extremely important due to their ability to win the game by goal. See also  Goal.

Rank
One of eight rows on an Arimaa board. Gold begins the game with 16 pieces on the first and second ranks while Silver beings with 16 pieces on the seventh and eighth ranks. The home rank for Gold is 1, while Silver's is 8.

Replacement
When a piece involved with holding a blockade or  frame is freed to move by replacing it with another (usually weaker) friendly piece. Also referred to as rotation.

Sacrifice
If a player allows a friendly piece to be trapped in order to pursue a strategic objective elsewhere on the board, the friendly piece is said to be sacrificed.

Scatter
When a player's home trap is invaded the pieces near that trap move away to avoid being captured. See also  Invade.

Setup
The opening phase of the game during which Gold then  Silver places the pieces on their first 2 rows, respectively.

Silver
The player with the Silver pieces is second to setup the pieces and second to move. See also  Gold.

Step
A player may use between one and four steps on any turn. Moving a piece requires one step, while an additional step is required for a push or  pull (a total of two steps).

Swarm
When a group of pieces advance together to overwhelm or  blockade a stronger enemy piece.

Trap (noun)
There are 4 trap squares on the board located at c3, c6, f3 and f6. Pieces that occupy these four squares may be trapped. See also  Trap (verb).

Trap (verb)
A piece is trapped and removed from the board if it occupies a trap square and there are no friendly pieces occupying any of the four adjacent squares. If there is a friendly piece on an adjacent square, then it is possible for a second piece to safely walk over - or occupy - on a trap square. A trapped piece can also be described as being captured. See also  Trap (noun).

Turn
A player completes a turn by moving pieces a total of one, two, three or four legal steps. The opposing player then makes his/her turn. Also known as a move. See also  Step.

West Wing
The left side of the board viewed from Gold's perspective, specifically the a-, b-, and c-files.