underbite
noun [ C or U ] uk/ˈʌn.də.baɪt/ us/ˈʌn.dɚ.baɪt/
反颌（指下颌或下门齿前突，超出上颌或上门齿）
the position of the teeth in which the lower teeth go over the upper teeth when a person bites the teeth together, or the degree to which the lower teeth are in front of the upper teeth
Compare: overbite