Noun, originating somewhere in the Pacific Northwest. A girl who is superlatively awesome, exerting her superiority wherever she goes (but in a non-pretentious manner; more of a transcendent, aloof hipness). Possible association with "terminator," though in an innocuous (not lethal) sense.
Alternately: An enigmatic and delightful person.
Partygoers felt keenly aware of their superficiality when a janinator walked into the room.