Model mate

A checkmate position, in which each king-fligt is blocked or guarded only once, and all the units of the opposite colour (with the allowable exceptions of the king and pawns) take part by guarding a flight or by pinning a piece that would otherwise prevent the mate. Pin of a piece on a square adjacent to the king is also allowed, even though that square is both blocked and guarded. [FIDE Album]

In the The Oxford Companion to Chess, David Hooper and Kenneth Whyld gave a more complex definition, allowing for exceptions in the cases of pins and double check:

Model mate is a pure mate in which all the attacker's men, with the possible exception of king and pawns, take part. Pure mate is a checkmate that meets the following criteria:

• unoccupied squares in the king's field are attacked once only;
• pieces that function as self-blocks are not under attack unless necessarily pinned;
• and the mating move is not a double check unless this is necessary to prevent the defender from interposing a man or capturing a checking piece.

See also: Ideal mate.