形容词难以预测的; 难以预料的，未定局的; 怀疑的，拿不准的; 不明不白
doubtful
形容词
2. It is doubtful that he will come.
他会不会来值得怀疑。
3. I'm doubtful whether she's still alive.
我怀疑她是否还健在。
4. He is a doubtful character.
他是一个不可靠的人。
1. 可疑的：1907年,AMA把当时160所医学院分成可接受(Acceptable)、可疑的(Doubtful)、不可接受(Unacceptable)三类. 很多美国医生对AMA日益因循守旧、自私自利的姿态非常不满,他们不但不参加AMA,而且还成立了自己的组织,与AMA针锋相对,反其道而行之.
2. 表示不是很肯定：◆positively adv. 绝对地,完全地 | doubt; doubtful; uncertain; dubious 表示不是很肯定 | ◆disadvantage n. 短处,缺点
3. 怀疑的,可疑的：doubt 怀疑,疑问,不相信 | doubtful 怀疑的,可疑的 | doubtless 无疑的,很可能的
1. 未必的;不大可能的
If it is doubtful that something will happen, it seems unlikely to happen or you are uncertain whether it will happen.
e.g. For a time it seemed doubtful that he would move at all...
有一段时间他似乎根本不会搬家。
e.g. It is doubtful whether Tweed, even with his fluent French, passed for one of the locals...
尽管特威德能说一口流利的法语，他是否能被当作当地人还很难说。
2. 怀疑的;疑惑的;拿不定主意的
If you are doubtful about something, you feel unsure or uncertain about it.
e.g. I was still very doubtful about the chances for success...
我对能否成功仍然深表怀疑。
e.g. Why did he sound so doubtful?
为什么他听上去如此不确定？
3. (质量或价值)低劣的，不可靠
If you say that something is of doubtful quality or value, you mean that it is of low quality or value.
doubtful的近义词
e.g. ...selling something that is overpriced or of doubtful quality...
售卖漫天要价或质量低劣的东西
e.g. They also seemed of very doubtful value.
它们好像也没有多大价值。
4. (通常指运动员因伤)不大可能参加（比赛）的
If a sports player is doubtful for a match or event, he or she seems unlikely to play, usually because of injury.
e.g. Forsyth is doubtful for tonight's game with a badly bruised leg.
福赛斯腿部严重擦伤，不大可能参加今晚的比赛。