It's equivalent to a shot at a ball you can't hit, e.g. buried deep in the grass or underneath lignified heather. Unfortunately, we have no "unplayable", so there's a few other options:
- find the way out of the mess, to the side or back,
- quit the game,
- use balls until the hole is maxed out (10 to 15 shots = 5 to 7 balls),
- apply soft putts until the hole is maxed out (10 to 15 shots) - this is said to save balls.