In general if some terminology exists for an object, the complementary object is called the co-object (assuming it exists).
For the purpose of my research it is very useful to define graphs in reversed order, that is, {(y, x) such that y = f(x)}. I simply referred to them as graphs until now, but the time has come to name them something better! (As much as I would like to, I can't call them "graphs" because they're literally not graphs. I also feel that cograph isn't quite correct although I like the ring of it.)
Thank you