IMPER'FECT, adjective [Latin imperfectus; in and perfectus, finished, perfect; perficio, to perfect; per and facio, to make.]

1. Not finished; not complete. The work or design is imperfect

2. Defective; not entire, sound or whole; wanting a part; impaired. The writings of Livy are imperfect

3. Not perfect in intellect; liable to err; as, men are imperfect; our minds and understandings are imperfect

4. Not perfect in a moral view; not according to the laws of God, or the rules of right. Our services and obedience are imperfect

5. In grammar, the imperfect tense denotes an action in time past, then present, but not finished.

6. In music, incomplete; not having all the accessary sounds; as an imperfect chord.

An imperfect interval is one which does not contain its complement of simple sounds.