WordNet records no synonym and no antonym for trespass on the case. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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.
an action brought to recover damages from a person whose actions have resulted indirectly in injury or loss
“a person struck by a log as it was thrown onto a road could maintain trespass against the thrower but one who was hurt by stumbling over it could maintain and action on the case”
Synonyms, antonyms and the broader and narrower relations for trespass on the case come from Princeton University’s WordNet. Full sources and licences.