The 'Triangle Mate' ('Fish Tail Mate')
The 'Triangle' ('Fishtail') checkmate is delivered by a queen and rook to a blocked King. The King doesn't necessarily need to be on the edge of the board but must be blocked by its own piece (or pieces). The main characteristic of this mate is that the pieces form a triangle shape (which also looks like a fish tail hence the alternative name 'Fishtail').