twinpeaks, I also thought "step change" was contemporary mgt...

twinpeaks, I also thought "step change" was contemporary mgt jargon. It is a bit, but the phrase apparently originates from mathematics. It's even defined in the Oxford dictionary!
http://en.wiktionary.org/wiki/step_change
http://oxforddictionaries.com/definition/english/step%2Bchange

Basically, as estseon said, its a sudden change, particularly a faster pace of growth. Visualize a dog leg trend line, where the angle suddenly has a steeper angle.

Incidentally, one of my favourite jargon obfuscations was by Bob Nardelli just after he became the short-lived CEO of Chrysler:
"I’m blessed to have individuals with me who can take areas of responsibility and do vertical dives to really get the granularity and make sure that we're coupling horizontally across those functions so that we have a pure line of sight toward the customer.”