Third person singular of defuse; to reduce tension in a situation or to remove a fuse from an explosive device to prevent detonation.
From 'defuse,' which combines 'de-' (remove) and 'fuse' (the ignition device or the state of tension). The word emerged in mid-20th century, first in military contexts, then metaphorically.
The difference between 'defuse' and 'diffuse' confuses many people—defuse means to remove danger, while diffuse means to spread out, but they're completely different words with different roots.
Complete word intelligence in one call. Free tier — 50 lookups/day.