I propose to change the definition of 'attack' by the following:

1. A piece is under attack when the opponent, would it be his turn, could *legally* capture it in the current position.
2. A square is under attack from a player when that player could *legally* capture an enemy piece standing on that square, given the remaining board occupation.
3. Colloquially, 'to attack' can also mean "play a move that creates one of the above situations".

Where *legally* would refer to the term 'legal', defined as:

Moves are legal when they would comply with all rules of the game. Moves are called pseudo-legal when they they comply with all rules except those that forbid to leave certain pieces (usually called *royals*) exposed to capture after a move.

Where *royals* would refer to an entry for 'royal':

A piece type is called 'royal' when capture or elimination of it terminates the game. With only a single royal per player, capture implies elimination. In some CVs a player can have multiple royals. We can then distinguish absolute royalty (first capture of a royal terminates the game) from extinction royalty (elimination of all royals of one player forces game termination).

CVs often have the rule that it is not *legal* to expose yourself to a game-terminating move of the kind described above that would result in your loss. (See *check*, *mate*.) In this case the mentioned captures cannot be part of any real game, and are only used as hypothetical continuations after moves that are not legal, to establish their illegality.

And for 'check':

A player on move is said to be 'in check' when his opponent, if he were on move, would be able to instantly decide the game in his advantage by capturing a *royal* piece.

(The condition that the capture should be a win is added to exclude cases like Tai Shogi, where capture of a royal by an Emperor would be a loss if recapture is possible. The word instantly was added to exclude situations where the capture of one of multiple royals is merely the first move of a forced winning line. Perhaps the term 'instantly decide' should be replaced by 'terminate', which could then get its own definition in the glossary.)

For 'mate':

A position where the player on move has no *legal* move is called a 'mate'. We distinguish checkmate (when mentioned player is also in *check*) and stalemate (otherwise), and the rules of the CV often assign a different result to those.

Possible entry for 'terminate':

A move is said to terminate a game if it fixes the game result without the players having to play any more moves. This does not exclude that the move is followed by a number of automatic hypothetical moves ('*after-moves*') to determine that the termination condition is indeed fulfilled, and what the game result should be. (E.g. *checkmating* terminates an orthodox Chess game, but two more hypothetical half-moves would have to follow to establish whether the royal can indeed not escape capture.)

After-move:

An after-move is a move in a hypothetical continuation of a *terminated* game for the purpose of determining whether the termination condition was fulfilled, was reached through a move that was *legal*, or what the game result is. E.g. when *baring* the opponent King is a winning game-terminating condition, an after-move can be needed to establish whether the capture that achieved it did not put your own King in *check*. If the result should be adjusted to draw when the bared opponent can counter-bare you through a legal move, two after-moves are needed. In this respect baring differs from capture of a *royal*, which typically does not allow an after-move, and thus never exposes your own royal to anything, so that any pseudo-legal move is also legal. The number of after-moves that should be taken into consideration, and their effect on the game result, is an essential part of definition of the winning condition.