oregano UK /ˈɒɹɪˌɡɑːnəʊ/US /əˈɹɛɡənoʊ/ noun3 •A herb of the mint family, Origanum vulgare, having aromatic leaves. •The leaves of these plants used in flavouring food. •Other herbs with a similar flavor, including other species in the genus Origanum, and Mexican oregano, Lippia graveolens. formsoreganos