rara avisEnglishOxford American Thesaurusrara avis noun Latin a man of integrity in high office is something of a rara avis: rarity, rare person/thing, rare bird, wonder, marvel, nonpareil, nonesuch, one of a kind, find; anomaly, curiosity, oddity, aberration, freak; outlier, edge case; British, informal one-off, oner.