heir presumptive
英 [ˌeə prɪˈzʌmptɪv] 
美 [ˌer prɪˈzʌmptɪv]
n. 假定继承人(其继承权会因有血统更近的继承人出生而丧失)
法律
牛津词典
noun
- 假定继承人（其继承权会因有血统更近的继承人出生而丧失）
an heir who may lose his or her legal right to receive sb's property, money or title if sb with a stronger claim is born
英英释义
noun
- a person who expects to inherit but whose right can be defeated by the birth of a nearer relative