[1] : The Collaborative International Dictionary of English v.0.48

imperfect \imper"fect\, a. l. imperfectus: pref. im- not +
   perfectus perfect: cf. f imparfait, whence oe. imparfit. see
   perfect.
   1. not perfect; not complete in all its parts; wanting a
      part; deective; deficient.
      1913 webster

            something he left imperfect in the state. --shak.
      1913 webster

            why, then, your other senses grow imperfect. --shak.
      1913 webster

   2. wanting in some elementary organ that is essential to
      successful or normal activity.
      1913 webster

            he . . . stammered like a child, or an amazed,
            imperfect person.                     --jer. taylor.
      1913 webster

   3. not fulfilling its design; not realizing an ideal; not
      conformed to a standard or rule; not satisfying the taste
      or conscience; esthetically or morally defective.
      1913 webster

            nothing imperfect or deficient left
            of all that he created.               --milton.
      1913 webster

            then say not man's imperfect, heaven in fault;
            say rather, man's as perfect as he ought. --pope.
      1913 webster

   imperfect arch, an arch of less than a semicircle; a skew
      arch.

   imperfect cadence mus., one not ending with the tonic,
      but with the dominant or some other chord; one not giving
      complete rest; a half close.

   imperfect consonances mus., chords like the third and
      sixth, whose ratios are less simple than those of the
      fifth and forth.

   imperfect flower bot., a flower wanting either stamens or
      pistils. --gray.

   imperfect interval mus., one a semitone less than
      perfect; as, an imperfect fifth.

   imperfect number math., a number either greater or less
      than the sum of its several divisors; in the former case,
      it is called also a defective number; in the latter, an
      abundant number.

   imperfect obligations law, obligations as of charity or
      gratitude, which cannot be enforced by law.

   imperfect power math., a number which can not be produced
      by taking any whole number or vulgar fraction, as a
      factor, the number of times indicated by the power; thus,
      9 is a perfect square, but an imperfect cube.

   imperfect tense gram., a tense expressing past time and
      incomplete action.
      1913 webster
see also:
perfect imperfect arch imperfect cadence imperfect consonances imperfect flower imperfect interval 
imperfect number defective number abundant number imperfect obligations imperfect power 
imperfect tense 

[2] : WordNet (r) 2.0

imperfect tense
     n : a tense of verbs used in describing action that is on-going
         syn: progressive, progressive tense, imperfect, continuous
         tense
see also:
progressive progressive tense imperfect continuous tense 

Tense >> T Words
Tense, definition of term: Tense
tense_pag1.html

Imperfect >> I Words
Imperfect, definition of term: Imperfect
imperfect_pag1.html

Perfect Tense >> P Words
Perfect Tense, definition of term: Perfect Tense
perfect+tense_pag1.html

Past Tense >> P Words
Past Tense, definition of term: Past Tense
past+tense_pag1.html

Future Tense >> F Words
Future Tense, definition of term: Future Tense
future+tense_pag1.html