tatsoi Syllabification: (tat·soi)Pronunciation: /tatˈsoi/Definition of tatsoi noun a kind of Chinese cabbage with glossy dark green leaves. Brassica rapa variety rosularis Origin:Chinese daat-choi, from daat- 'sink, fall flat' + choi 'vegetable'tatsoi in other Oxford dictionaries Definition of tatsoi in the British & World English dictionary