If it is doubtful that something will happen, it seems unlikely to happen or you are uncertain whether it will happen.
For a time it seemed doubtful that he would move at all.
短期内他似乎根本不会搬走。
If you are doubtful about something, you feel unsure or uncertain about it.
dubious
I was still very doubtful about the chances for success.
我仍然不能肯定成功的可能性有多大。
If you say that something is of doubtful quality or value, you mean that it is of low quality or value.
selling something that is overpriced or of doubtful quality.
销售价格过高或质量有问题的东西。
If a sports player is doubtful for a match or event, he or she seems unlikely to play, usually because of injury.
Forsyth is doubtful for tonight's game with a badly bruised leg.
福赛斯因为严重的腿伤不太可能参加今晚的比赛。