iota souscritcommon nounEtymologyexpandsee iota and subscript.Definition1. Diacritical mark of Ancient Greek composed of a small iota placed under a long vowel to indicate a diphthong, giving ᾳ, ῃ, and ῳ for lowercase and ᾼ, ῌ, and ῼ for uppercase.expandOriginellement, l'iota souscrit note une diphtongue dont le premier élément est long.