WordNet records no synonym and no antonym for yardie. 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.
member of an international gang of Jamaican criminals who sell drugs and violence
“A much publicized raid on a yardie stronghold had first been simulated at Riot City”
Synonyms, antonyms and the broader and narrower relations for yardie come from Princeton University’s WordNet. Full sources and licences.