From Middle English imperfit, from Old French imparfit (modern French imparfait), from Latin imperfectus.

• (adjective) IPA: /ɪmˈpɜː(ɹ)fɪkt/, /ɪmˈpɜː(ɹ)fɛkt/
• (verb) IPA: /ɪmpə(ɹ)ˈfɛkt/

imperfect

1. not perfect

   Synonyms: defective, fallible, faultful, faulty

   Antonyms: faultless, infallible, perfect

   • c. 1603–1606, William Shakespeare, “The Tragedie of King Lear”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC ↗, [Act IV, scene vi]:

     Why, then, your other senses grow imperfect.

   • 1667, John Milton, “Book VIII”, in Paradise Lost. […], London: […] [Samuel Simmons], and are to be sold by Peter Parker […]; [a]nd by Robert Boulter […]; [a]nd Matthias Walker, […], →OCLC ↗; republished as Paradise Lost in Ten Books: […], London: Basil Montagu Pickering […], 1873, →OCLC ↗:

     Nothing imperfet or deficient left
     Of all that he Created.

   • 1733, [Alexander Pope], An Essay on Man. […], (please specify |epistle=I to IV), London: Printed for J[ohn] Wilford, […], →OCLC ↗:

     Then say not man's imperfect, Heaven in fault; / Say rather, man's as perfect as he ought.

2. (botany) unisexual: having either male (with stamens) or female (with pistil) flowers, but not with both.

   Antonyms: perfect

3. (taxonomy) known or expected to be polyphyletic, as of a form taxon.
4. (obsolete) lacking some elementary organ that is essential to successful or normal activity.
   • 1653, Jeremy Taylor, “Twenty-five Sermons Preached at Golden Grove; Being for the Winter Half-year, […]: Sermon III. [Doomsday Book; or, Christ’s Advent to Judgment.] Part III.”, in Reginald Heber, editor, The Whole Works of the Right Rev. Jeremy Taylor, D.D. […], volume V, London: Ogle, Duncan, and Co. […]; and Richard Priestley, […], published 1822, →OCLC ↗, page 35 ↗:

     When the prophet Joel was describing the formidable accidents in the day of the Lord's judgment, and the fearful sentence of an angry Judge, he was not able to express it, but stammered like a child, or an amazed, imperfect person.

5. (grammar) belonging to a tense of verbs used in describing a past action that is incomplete or continuous

• imperfection

• German: unvollkommen, mangelhaft, unvollständig, fehlerhaft
• Italian: imperfetto, imperfetta
• Portuguese: imperfeito
• Russian: несоверше́нный
• Spanish: imperfecto

imperfect (plural imperfects)

1. something having a minor flaw
2. (grammar) a tense of verbs used in describing a past action that is incomplete or continuous

   Synonyms: preterimperfect

• French: imparfait
• German: Imperfekt, Imperfektum
• Italian: imperfetto
• Portuguese: imperfeito
• Russian: имперфе́кт
• Spanish: imperfecto

imperfect (imperfects, present participle imperfecting; simple past and past participle imperfected)

1. (transitive) to make imperfect
   • 1651, John Donne, Letter to Henry Goodere, in Letters to Severall Persons of Honour, edited by Charles Edmund Merrill, Jr., New York: Sturgis & Walton, 1910,

     I write to you from the Spring Garden, whither I withdrew my self to think of this; and the intensenesse of my thinking ends in this, that by my help Gods work should be imperfected, if by any means I resisted the amasement.

   • 1962, Alec Harman, Wilfrid Mellers, Man and His Music: The Story of Musical Experience in the West‎, Oxford University Press, Part I, Chapter 5, p. 126:

     […] such was their desire for greater rhythmic freedom that composers began to use red notes as well. […] Their value was […] restricted at first, for redness implies the imperfecting of a note which is perfect if black […]