System-to-System processes, in this context, refer to process involving systems only.

The Umbrellas can refer to several things involving umbrellas:

Correlation refers to any of a broad class of statistical relationships involving dependence.

First amendment law referring to cases and precedent involving the first amendment.

Verbal memory is a term used in cognitive psychology that refers to memory of words and other abstractions involving language.

Commodity market refers to physical or virtual transactions of buying and selling involving raw or primary commodities.

Melt-down - refers to any number of tricks involving each hand moving from a crosser to a waist-wrap position in a continuously alternating fashion.

American patriotism refers to patriotism involving cultural attachment of Americans to the United States as their homeland.

But for physicists, these words refer to much more indirect measurements involving a train of theoretical logic by which we can interpret what is "seen."

The term is also used in the Southern United States referring to deceit or mischief involving lies.