The Collaborative International Dictionary of English v.0.48:

Imp \Imp\ ([i^]mp), n. [OE. imp a graft, AS. impa; akin to Dan.
   ympe, Sw. ymp, prob. fr. LL. impotus, Gr. ? engrafted,
   innate, fr. ? to implant; ? in + ? to produce; akin to E. be.
   See 1st In-, Be.]
   1. A shoot; a scion; a bud; a slip; a graft. [Obs.]
      --Chaucer.
      [1913 Webster]

   2. An offspring; progeny; child; scion. [Obs.]
      [1913 Webster]

            The tender imp was weaned.            --Fairfax.
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   3. A young or inferior devil; a little, malignant spirit; a
      puny demon; a contemptible evil worker.
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            To mingle in the clamorous fray
            Of squabbling imps.                   --Beattie.
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   4. Something added to, or united with, another, to lengthen
      it out or repair it, -- as, an addition to a beehive; a
      feather inserted in a broken wing of a bird; a length of
      twisted hair in a fishing line. [Obs. or Prov. Eng.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Imp \Imp\, v. t. [imp. & p. p. Imped; p. pr. & vb. n.
   Imping.] [AS. impian to imp, ingraft, plant; akin to Dan.
   ympe, Sw. ympa, OHG. impf[=o]n, impit[=o]n, G. impfen. See
   Imp, n.]
   1. To graft; to insert as a scion. [Obs.] --Rom. of R.
      [1913 Webster]

   2. (Falconry) To graft with new feathers, as a wing; to
      splice a broken feather. Hence, [Fig.]: To repair; to
      extend; to increase; to strengthen; to equip. [Archaic]
      [1913 Webster]

            Imp out our drooping country's broken wing. --Shak.
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            Who lazily imp their wings with other men's plumes.
                                                  --Fuller.
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            Here no frail Muse shall imp her crippled wing.
                                                  --Holmes.
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            Help, ye tart satirists, to imp my rage
            With all the scorpions that should whip this age.
                                                  --Cleveland.
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WordNet (r) 3.0 (2006):

imp
    n 1: (folklore) fairies that are somewhat mischievous [syn:
         elf, hob, gremlin, pixie, pixy, brownie, imp]
    2: one who is playfully mischievous [syn: imp, scamp,
       monkey, rascal, rapscallion, scalawag, scallywag]

Moby Thesaurus II by Grady Ward, 1.0:

114 Moby Thesaurus words for "imp":
   Ariel, Befind, Corrigan, Dingbelle, Fifinella, Finnbeara, Hob,
   Hobgoblin, JD, Mab, Oberon, Puck, Titania, appendage, arm, bad boy,
   bad fairy, bad peri, banshee, booger, bough, branch, brat, brownie,
   buffoon, bugger, cluricaune, cutup, devil, deviling, devilkin,
   diablotin, dwarf, elf, enfant terrible, erlking, fairy,
   fairy queen, fay, funmaker, gamin, gnome, goblin, gremlin, hand,
   hob, hobgoblin, holy terror, hood, hoodlum, hooligan, joint, joker,
   jokester, juvenile delinquent, knave, kobold, leg, leprechaun,
   limb, link, little devil, little monkey, little rascal, lobe,
   lobule, member, minx, mischief, mischief-maker, monkey, offshoot,
   organ, ouphe, peri, pinion, pixie, poltergeist, pooka,
   practical joker, prankster, puca, puck, punk, punk kid, pwca,
   ramification, rapscallion, rascal, rogue, rowdy, ruffian, runner,
   scamp, scapegrace, scion, spoiled brat, spray, sprig, sprite, spur,
   switch, sylph, sylphid, tail, tendril, tokoloshe, troll, twig,
   urchin, wag, whippersnapper, wing, young devil



V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

IMP
       Interface Message Processors (ARPANET, MILNET)


The Free On-line Dictionary of Computing (30 December 2018):

IMP

   1.  IMProved Mercury autocode.

   2.  An extensible dialect of ALGOL 60, for CDC
   1604.

   ["Experience with an Extensible Language", Edgar T. Irons,
   CACM 13(1):31-39, Jan 1970].

   3.  Interpretive Menu Processor.

   4.  IMPlementation language.

   5.  Interface Message Processor.

   (1996-04-07)