Also seen spelled the French way: coup de grâce. Literally: a stroke of mercy. In that sense, it’s a little morbid. Commonly seen used in relation to the battlefield, it means the final shot or blow delivered to someone suffering with mortal injuries. However, in the day-to-day combat of life, it’s a little less frightening and used to describe a certain finishing act, blow or event.
Example: Jill, the sole owner’s representative at the weekly construction meetings, had held her wits about her during the project’s five month disastrous duration; however, she finally exploded in rage when the general contractor delivered the coup de grace: the painting subcontractor had disappeared, and with him, the rest of her client’s money.