"It would seem that "growth hacking" falls much more into the territory of pure Silicon Valley/startup ecosystem jargon. It's used by the same folks who say they're "killing it" and that they've "pivoted" and that they've "bootstrapped" despite having funding sources. Far more importantly, it's used to refer to classic marketing tactics - leveraging consumer psychology to create more viral funnels."

Source: Rand Fishkin via Moz

Rand Fishkin is the founder and former CEO of Moz, board member at presentation software startup Haiku Deck, co-author of a pair of books on SEO, and co-founder of Inbound.org.