/ˈdaʊtfl ||; ˈdaυtfəl/adj1 unlikely or uncertain 不大可能；不确定: It's doubtful whether/if we'll finish in time. 我们能否按时完成还不一定。It was doubtful that he was still alive. 他不大可能仍在人世了。
2 doubtful (about sth/about doing sth) (used about a person) not sure （指人）不能肯定:
He still felt doubtful about his decision. 自己的决定是对的还是不对的，他还拿不准。 ➔doubtfully /-fəli ||; -fəlɪ/ adv ‘I suppose it'll be all right,’ she said doubtfully. 她将信将疑地说﹕“我想不会有事吧。”