dimorphothecaPronunciation: /ˌdʌɪmɔːfəˈθiːkə/Definition of dimorphotheca noun a southern African plant of the daisy family, sometimes grown as a border plant. Genus Dimorphotheca, family Compositae (in gardening) any of a number of plants of the genus Osteospermum that are similar to dimorphothecas. Origin:modern Latin, from Greek dimorphos 'having two forms' + theca