diffuse

Concise Oxford English Dictionary © 2008 Oxford University Press:
diffuse

▶verb /dɪˈfjuːz/ spread over a wide area.

■ Physics intermingle with another substance by movement of particles.

▶adjective /dɪˈfjuːs/ 

• 1 spread out over a large area; not concentrated.

  ■ (of disease) not localized in the body.

• 2 lacking clarity or conciseness.

– derivatives
diffusely /dɪˈfjuːsli/ adverb,
diffuseness /dɪˈfjuːsnɪs/ noun,
diffuser (also diffusor) noun,
diffusible adjective.

– origin ME: from L. diffus-, diffundere ‘pour out’; the adj. is via Fr. diffus or L. diffusus ‘extensive’.

usage: The verbs diffuse and defuse sound similar but have different meanings. Diffuse means ‘spread over a wide area’, while defuse means ‘reduce the danger or tension in’. Thus sentences such as Cooper successfully diffused the situation are wrong, while Cooper successfully defused the situation would be correct.