In commentaries of professional games, the term losing move is used for the move at which the eventual loser still had his chances, but chose a clearly inferior play. The winner next made no mistakes so that even if the loser didn't make any either, he still could not recover the loss.
Sometimes magazine commentaries, for example in the now-defunct Kido, concentrate on the losing move - the point of no return in the game. This is however not so useful for amateur study, since it mostly says 'disregard anything that happens next'. Trying to identify the losing move in your own games can be a useful idea for self study.