IMPERFECT
Text: Not perfect. 1) An imperfect interval is one which is a semitone less than perfect. 2) The imperfect consonances are the third and sixth, as opposed to the fourth and fifth. 3) An imperfect cadence is one which does not give complete rest in key. All cadences not having a dominant or subdominant penultimate are said to be imperfect.
See Also:
Source: 125