WordNet records no synonym and no antonym for sky burial. 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.
a traditional Tibetan funeral ritual in which the corpse is exposed to the open air to be eaten by sacred vultures
Synonyms, antonyms and the broader and narrower relations for sky burial come from Princeton University’s WordNet. Full sources and licences.