Pure mate

A pure mate is a checkmating position in chess in which the mated king and all vacant squares in its field are attacked only once, and squares in the king's field occupied by friendly units are not also attacked by the mating side (unless such a unit is necessarily pinned to the king to avoid it interposing to block the check or capturing of mating unit).
Although several famous games ended in them, such as the Immortal Game, Evergreen Game, Peruvian Immortal, and Game of the Century, pure mates are of only incidental interest in practical play, but they are considered by some to add value to a chess problem.
If all units of the mating side, with the possible exception of the king and pawns, are involved in a pure mate, then it is a "model mate"; if all units of both colours are involved in a pure mate, then it is an "ideal mate".