It is the last definition that I use most often when coaching. Of course it does depend upon on recognising all the threats in the position, and there are plenty of endings that have ended in checkmate.
A kind of counter-example (in a different sense) turned up from last nights first round of the London Chess Classic (the reason why this post is late btw). The Grischuk - Nakamura game started off with a Berlin Defence to the Ruy Lopez (which is an opening known for a quick transition to an ending). On move 18 Grischuk decided that the king could be used as a fighting piece and moved it up the board. This was a brave decision as there were still plenty of pieces on the board (2R+3 minors each), and it was no surprise that found itself surrounded 10 moves later. However Grischuk had just enough the avoid getting mated and in the end Nakamrua had a repetition but no more.
Grischuk,Alexander - Nakamura,Hikaru [C67]
London Chess Classic Olympia, London (1.5), 04.12.2015