Hangfire
A perceptible delay between the trigger pull (and primer ignition) and the actual discharge. Range can be tenths of a second; safety implications are serious.
A hangfire feels like a normal fire that doesn’t immediately happen. The rifle is hot, the primer struck, but the round didn’t go. Convention says: keep the rifle pointed downrange for 30 seconds before opening the action, in case the round fires late.
Modern factory ammunition has hangfire rates near zero. They’re more often seen in old surplus ammo, contaminated handloads, or cartridges stored badly. Treat every misfire as a potential hangfire.