Definitions of cascade:

• noun:   a succession of stages or operations or processes or units

  Example: "Progressing in severity as though a cascade of genetic damage was occurring"

• noun:   a small waterfall or series of small waterfalls
• noun:   a sudden downpour (as of tears or sparks etc) likened to a rain shower

  Example: "A sudden cascade of sparks"

• verb:   rush down in big quantities, like a cascade
• verb:   arrange (open windows) on a computer desktop so that they overlap each other, with the title bars visible