牛油 (niúyóu, literally 'cow oil') is the Cantonese/Hong Kong word for butter.
植物牛油 is therefore literally 'vegetable butter'. Mainland speakers more often use
黄油 (huángyóu) for butter and
人造黄油 (rénzào huángyóu, 'artificial butter') or
麦淇淋 (màiqílín, transliteration) for margarine.
