incompatible has 10 distinct synonyms spread across 6 of its 9 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is compatible.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
not compatible
“incompatible personalities”
used especially of drugs or muscles that counteract or neutralize each other's effect
not suitable to your tastes or needs
“the uncongenial roommates were always fighting”
incapable of being used with or connected to other devices or components without modification
of words so related that one contrasts with the other
“`rich' and `hard-up' are contrastive terms”
not easy to combine harmoniously
not compatible with other facts
not in keeping with what is correct or proper
“completely inappropriate behavior”
1 of the 9 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for incompatible.
Synonyms, antonyms and the broader and narrower relations for incompatible come from Princeton University’s WordNet. Full sources and licences.