A person who is seemingly incapable of answering a question based upon a hypothetical situation due to what they deem a lack of realism
Tom: Hey Jim, if you were on a desert island and only had three objects with you what would they be?
Jim: Well how did I get to the desert island?
Tom: I dunno, you just appeared there I guess
Jim: That's not possible, and where are these objects coming from anyway? Why can't I take more stuff with me?
Tom: Dude, you're such a hypothetitard