defuse
To calm down a dangerous or tense situation before trouble.
To defuse means to make a dangerous or tense situation less threatening or explosive. The word originally referred to removing the fuse from a bomb so it couldn't explode. Bomb experts carefully defuse explosive devices by disconnecting the trigger mechanism, working with steady hands and complete focus because one mistake could be deadly.
Today we use defuse more broadly for calming down any volatile situation. When two friends are arguing heatedly, a third friend might defuse the conflict by cracking a joke or suggesting they take a break. A teacher might defuse classroom tension by acknowledging everyone's feelings and proposing a fair solution. Parents sometimes defuse a tantrum by staying calm and redirecting attention.
The key idea is removing the explosive potential before anything blows up. You're not ignoring the problem or pretending it doesn't exist. You're actively working to reduce the danger or intensity. Someone with skill at defusing situations can sense when emotions are running too high and knows how to cool things down before anyone says or does something they'll regret.
Don't confuse defuse with diffuse, which means to spread out or scatter. You defuse a bomb or an argument, but light diffuses through a room.