Mike,
I think Killian and Nugent's definition pretty much says it all and was well explained in TEPaul's posts. The golf digest explanation seems to have more to do with balance than values, as does Matt's, and encompasses more than the value of a single shot.
On one specific occasion I was before a zoning board with a road plan for a small subdivision. The code called for "Traffic Bound Gravel" to be used and my representative asked for a definition and clarification of the term. The board asked their engineer who could not find one anywhere. Finally my engineer, who had been sitting there smiling the whole time, chimed in. He said: " traffic bound gravel is gravel bound by traffic", end of quote, definition accepted by everyone.
Kind of like "Shot Values", the value of a shot.
Sometimes the simplest of answers is all that is needed to explain an idea or define a term.