Diffuse mean spread out, or the action of spreading out. If lots of people in school believe invisible angels are everywhere, you could say that opinion is diffuse. You might even think angels are diffuse as well.
As a verb, diffuse means to spread something out, but also applies to spreading things such as ideas or culture so that they become widely known. When something is diffused, it's mixed in, and when you drop propaganda pamphlets out of airplanes you're diffusing the propaganda. The adjective comes from Latin diffusus, from diffundere "to pour in different directions," from the prefix dis- "apart" plus fundere "to pour."
