WordNet records no synonym and no antonym for siegfried. 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.
(German mythology) mythical German warrior hero of the Nibelungenlied who takes possession of the accursed treasure of the Nibelungs by slaying the dragon that guards it and awakens Brynhild and is eventually killed; Sigurd is the Norse counterpart
Synonyms, antonyms and the broader and narrower relations for siegfried come from Princeton University’s WordNet. Full sources and licences.