incompatible

adjective

1. not compatible; specif.,
   1. not able to exist in harmony or agreement
   2. not going, or getting along, well together; incongruous, conflicting, discordant, etc.: often followed by with
2. that cannot be held at one time by the same person: said of positions, ranks, etc.
3. Logic
   1. that cannot both be true at the same time: said of propositions
   2. not predicable of the same subject without contradiction: said of terms
4. Math. logically contradictory: said of equations or other statements
5. Med., Pharmacy not suitable for being mixed or used together: said of substances having an undesirable action on each other or, when mixed, on the body

noun