tortoiseshell butterfly Syllabification: (tor·toise·shell but·ter·fly)Definition of tortoiseshell butterfly noun a butterfly with mottled orange, yellow, and black markings, and wavy wing margins. Genera Aglais and Nymphalis, subfamily Nymphalinae, family Nymphalidae: several species tortoiseshell butterfly in other Oxford dictionaries Definition of tortoiseshell butterfly in the British & World English dictionary