[DonThomasitos]

The difference to a deadlock is that a deadlock is a inability to move, the zugzwang is an obligation to move.

[alex43578]

An obligation to move to your disadvantage.

[Krasnol]

The disadvantage is the fact that you're obligated to move. The outcome of the move is not determined though.

[alex43578]

“Any legal move will worsen their position”, so the outcome of your move is determined to be inherently negative.

[layer8]

More accurately, it’s being forced to move a specific piece despite disadvantages, because not moving it would result in an even worse outcome — as opposed to moving a different piece that you’d otherwise prefer to move. So it means being forced to move that first piece instead of not moving it (instead of moving a different piece).

And that’s the generalized meaning in German, being forced to act with respect to a specific thing, where you’d normally prefer to keep it in its current state.

[Krasnol]

The word has it's use outside the chess world though and there it is as I wrote it.

[darkwater]

What happens if you don't move in chess? Honest question.

[tromp]

You run out of time on your clock. If you press your clock without moving, the opponent will alert the referee to sort you out. And if you play without a clock, your opponent will get annoyed at you taking forever to move.