WordNet records no synonym and no antonym for death seat. 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.
the car seat beside the driver of an automobile; believed to be the most dangerous place to sit in a car in case of an accident
Synonyms, antonyms and the broader and narrower relations for death seat come from Princeton University’s WordNet. Full sources and licences.