growth hacker (noun) - one who’s passion and focus is growth through use of a testable, empirical, and scalable methodology.
Basically, a growth hacker is the blend of a product, marketing, and data. They sort of operate as R&D within a startup.
Resources: http://www.quora.com/Growth-Hacking/What-is-growth-hacking/a... http://startup-marketing.com/where-are-all-the-growth-hacker... http://www.vlaskovits.com/2012/07/youre-a-growth-rookie-not-... http://www.aginnt.com/growth-hacker#.UDvRGmPlWPI