This week’s Word Nerd subject is another of those cases where using the wrong one can result in a sentence that says almost the exact opposite of what was meant.
Defuse: To remove or disable the triggering mechanism of an explosive device; metaphorically, to make a situation less dangerous or tense.
Diffuse: (verb) to scatter or disperse over a wide area.
(adjective) scattered or dispersed over a wide area.
Defuse is a modern word, dating from the World War II era. It’s a pseudo-Latin word, derived from the combination of the Latin prefix de-, meaning “to remove or take away” plus fuse, which comes from a 17th century Italian word, fuso, meaning spindle, a long thin tube. (The first fuses in munitions were reeds filled with gunpowder.)
Diffuse originates in the 1520s, and comes from the Latin diffusus, meaning “to pour out or away.”
Diffuse has two different pronunciations, depending on whether is being used as a verb or an adjective; when a verb (“the curtain will diffuse the sunlight”), it rhymes with blues, while the adjective (“a diffuse community”) rhymes with juice.
If you say “a little humor will diffuse hostilities” you’re saying that telling a joke will spread the hostilities and make everyone mad.
If you say “the shower door defuses the light,” you’re saying that the shower door keeps the light from exploding.