In chess a back-rank mate occurs on the board when a heavy piece (queen or rook) invades the opponent's last rank (the first rank for White or the eighth rank for Black). In this situation the king's own pawns (or other pieces) deprive it of squares to which it could retreat and cannot prevent the attack.
It's worth noting that this mate is a variation of the Corridor Mate. The main difference from other variations of the mate is that the checkmate is delivered along the last rank with the King blocked by its own pieces on the penultimate rank.