[ptspts]

Is there a precise, published-in-advance definition of cheating in the chess contest rules, or are the contest organizers allowed to shift goalposts as they see fit, and ban a player from future contests because of any arbitrary reason they come up with?

My naïve definition would be: a player was probably not cheating if they would have been able to come up with the same moves even if they had played in an isolated room with only basic supplies (such as water and sugar for human players and electricity for computer players). Thus a player who is consulting a chess book, a friend, the web or a computer is cheating, because those are not available in an isolated room.

[superhuzza]

Yes, if it's a FIDE tournament, there is a precise definition about what is allowed. Of course, this will be applied as interpreted by the arbiters.

12.3 a. During play the players are forbidden to make use of any notes, sources of information or advice, or analyse on another chessboard.

12.3 b. Without the permission of the arbiter a player is forbidden to have a mobile phone or other electronic means of communication in the playing venue, unless they are completely switched off. If any such device produces a sound, the player shall lose the game. The opponent shall win. However, if the opponent cannot win the game by any series of legal moves, his score shall be a draw.