non-committal
/ˌnɒnkəˈmɪtəl/adjective
- (of a person or a person's behaviour or manner) not expressing or revealing commitment to a definite opinion or course of action（人, 行为, 态度）不表态的; 不明朗的：
her tone was non-committal, and her face gave nothing away.
她的语气含糊, 脸上也没表露出什么。
派生词