What is the meaning of diffusion?

noun

• Physics) the process in which there is movement of a substance from an area of high concentration of that substance to an area of lower concentration. (
• The spread of social institutions (and myths and skills) from one society to another.
• The property of being diffused or dispersed.
  • synonyms: dissemination
• The act of dispersing or diffusing something.
  • usage: "the dispersion of the troops"; "the diffusion of knowledge"
  • synonyms: dispersion, dispersal, dissemination