WordNet records no synonym and no antonym for double leg circle. 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 gymnastic exercise performed on the pommel horse when the gymnast (with legs together) swings his legs in a circle while alternating hands on the pommels
Synonyms, antonyms and the broader and narrower relations for double leg circle come from Princeton University’s WordNet. Full sources and licences.