If something such as knowledge or information is diffused, or if it diffuses somewhere, it is made known over a wide area or to a lot of people.

To diffuse a feeling, especially an undesirable one, means to cause it to weaken and lose its power to affect people.

If something diffuses light, it causes the light to spread weakly in different directions.

To diffuse or be diffused through something means to move and spread through it.

Something that is diffuse is not directed towards one place or concentrated in one place but spread out over a large area.

If you describe something as diffuse, you mean that it is vague and difficult to understand or explain.