Plot armor
Etymology
A fan and critic term popularized through the TV Tropes wiki and online fandom discussion in the 2000s. The metaphor is that the plot itself acts as armor: the character survives not because it’s plausible but because the story can’t continue without them.
noun · /PLOT AR-mur/
A character’s implausible immunity from death or harm, because the story needs them to survive.
What it names
It names the invisible protection a narrative grants its essential characters — the reason the hero walks unscathed out of situations that would kill anyone else. It’s a handle for a specific kind of broken tension: you can’t fear for someone the plot won’t let die.
Example
The protagonist took three bullets and kept running — plot armor at its most shameless.
Related idea
Distinct from a deus ex machina, a one-off rescue: plot armor is the standing, unspoken guarantee that a key character simply cannot die.