An engineer with almost no personal startup ambition who sells his talents to the highest bidder. They are often silent unless spoken too and in many instances perceived as judging you without even hearing them speak a word. If your a startup founder, you must be ready to spend some serious coin to recruit one these guys and girls.
Even though he'd worked at Twitter for years building out many of their core products, he had no hesitation switching to Google X, when they offered him 10k more a year.