Diffuse/dɪˈfjuːs/ Definition 1 of 4Pro Tip 1/3Physical Spread Use 'diffuse' to describe things spread over physical spaces, like light or smell. The fog diffused across the harbor. Pro Tip 2/3Not Just Physical 'Diffuse' also explains the spread of intangible things, like ideas or trends. The new fashion trend diffused quickly through social media. Pro Tip 3/3Neutral Connotation The adjective form is neutral, it doesn't imply if being spread out is good or bad. The diffuse lighting created a soft ambiance in the café.