WordNet records no synonym and no antonym for geoffrey of monmouth. 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.
Welsh chronicler who wrote an account of the kings of Britain which is now believed to contain little historical fact but it is a source of the Arthurian legend (circa 1100-1154)
Synonyms, antonyms and the broader and narrower relations for geoffrey of monmouth come from Princeton University’s WordNet. Full sources and licences.