|an extraordinary or unusual thing, person, or event; an exceptional example or instance.|
|a children's mummer's parade, as on the Fourth of July, with prizes for the best costumes.|
isoantigen i·so·an·ti·gen (ī'sō-ān'tĭ-jən)
An antigenic substance present in some members of a species and capable of stimulating antibody production in those members that lack it. Also called alloantigen.