reify [from the Latin res (thing) + -fy]: to treat (an abstraction) as substantially existing, or as a concrete material object.As the dictionary suggests, to reify is to thing-ify: to treat what is not a thing as a thing. (This is the sense the word carries in Marx's definition of commodity fetishism: reification of persons, anthropomorphizing of things.) In academic writing, however, "reify" and "reification" have become vague, almost catch-all terms of disapproval, used to indicate disagreement with whatever the author doesn't like.
So many examples of this usage are available that to single out one is unfair, but there is one example that's fresh in my mind. Recently I was glancing through an article that draws on Marxian work in international relations "to recast the socio-historical conditions of emergence and diffusion of the modern national form" (F.G. Dufour, "Social-property Regimes and the Uneven and Combined Development of Nationalist Practices," European Journal of International Relations 13:4 , pp.583-604).
This article says there's a need to "move beyond the reification of a collective domestic identity" (p.588). I'm pulling this phrase out of context, because to supply the context would be rather tedious. But it is illustrative, I think, of the basic procedure: take an abstraction, assert that it's being reified, and you have a criticism that's often difficult if not impossible to refute, because it usually boils down to "I don't like the way scholar X is using this concept."