The terms ‘citizen science’ and ‘citizen scientist’ have been added to the OED. Here are the official definitions according to the dictionary:
citizen science n. scientific work undertaken by members of the general public, often in collaboration with or under the direction of professional scientists and scientific institutions.
citizen scientist n. (a) a scientist whose work is characterized by a sense of responsibility to serve the best interests of the wider community (now rare); (b) a member of the general public who engages in scientific work, often in collaboration with or under the direction of professional scientists and scientific institutions; an amateur scientist.
Sadly, there is no mention of the Zooniverse …yet. You can read more about their addition in this blog post by Prof. Muki Hacklay.