spheroplast Syllabification: (sphe·ro·plast)Pronunciation: /ˈsfi(ə)rəˌplast, ˈsfer-/Definition of spheroplast noun Biology a bacterium or plant cell bound by its plasma membrane, the cell wall being deficient or lacking and the whole having a spherical form. spheroplast in other Oxford dictionaries Definition of spheroplast in the British & World English dictionary