Mutually exclusive.
That contradicts something, such as an argument.
That is diametrically opposed to something.
That is itself a contradiction.
Tending to contradict or oppose, contrarious.
Either of a pair of propositions, that cannot both be true or both be false.
Corresponding; complementary.
Having the base, or end next to the attachment, narrower than the top.
Turned or facing toward the observer.
A proposition obtained by obversion, e.g. All men are mortal => No man is immortal.
The heads side of a coin, or the side of a medal or badge that has the principal design.