Definitions for obversionɒbˈvɜr ʒən, -ʃən
Random House Webster's College Dictionary
ob•ver•sionɒbˈvɜr ʒən, -ʃən(n.)
an act or instance of obverting.
a form of inference in which a negative proposition is obtained from an affirmative, or vice versa, as “None of us is immortal” is obtained by obversion from “All of us are mortal.”
Origin of obversion:
1840–50; < LL
the act of turning toward or downward
the act of immediate inference, by which we deny the opposite of anything which has been affirmed; as, all men are mortal; then, by obversion, no men are immortal. This is also described as "immediate inference by privative conception."