Herbert Benson's (199x) book was a landmark book in American culture because it popularized meditative practices previously not practiced to any great extent in Western culture. Many people bought, read, and were helped by Benson's book.
As we read it, Benson's definition, while not so scientific-sounding, harks back to the physics and engineering definition. Both seem to imply that stress involves forces external to the self --"a measurable applied force," "environmental demands." Stress is "out there," in the environment, implying that we humans are just the passive recipients of stress which happens to come our way.
But is that so? We are part of the environment we live in, shaping our own experience --in part, at least. So Benson's definition may not be adequate for our purposes here.