n the act of diffusing or dispersing something, or the property of being diffused or dispersed; dispersion
n (physics) the scattering of light by reflection from a rough surface, or by passage through a translucent medium
n (context|physics|weather) exchange | Exchange of airborne media between regions in space in an apparently random motion of a small scale.
n the movement of water vapor from regions of high concentration (high water vapor pressure) toward regions of lower concentration.