a.

1. 不完美的；有缺点的；有瑕疵的
   imperfect products

   有瑕疵的产品

2. 不完整的；残缺的；未完成的
   an imperfect knowledge of French

   对法语一知半解

3. 【语】未完成时的；未完成过去时的
4. 【音】不完全协和的

n.

1. 【语】未完成时（动词）；未完成过去时（动词）[the S][C]

adj.

1. faulty or incomplete.
2. Grammar  (of a tense) denoting a past action in progress but not completed at the time in question.
3. Music  (of a cadence) ending on the dominant chord.
4. Law  (of a gift, title, etc.) transferred without all the necessary conditions or requirements being met.