WordNet records no synonym and no antonym for theater of the absurd. 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.
plays stressing the irrational or illogical aspects of life, usually to show that modern life is pointless
“Samuel Beckett and Eugene Ionesco have written plays for the theater of the absurd”
Synonyms, antonyms and the broader and narrower relations for theater of the absurd come from Princeton University’s WordNet. Full sources and licences.