The Collaborative International Dictionary of English v.0.48:

Elves \Elves\, n.; pl. of Elf.
   [1913 Webster] Elvish \Elv"ish\, a.
   1. Pertaining to elves; implike; mischievous; weird; also,
      vacant; absent in demeanor. See Elfish.
      [1913 Webster]

            He seemeth elvish by his countenance. --Chaucer.
      [1913 Webster]

   2. Mysterious; also, foolish. [Obs.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Elf \Elf\ ([e^]lf), n.; pl. Elves ([e^]lvz). [AS. [ae]lf, ylf;
   akin to MHG. alp, G. alp nightmare, incubus, Icel. [=a]lfr
   elf, Sw. alf, elfva; cf. Skr. [.r]bhu skillful, artful, rabh
   to grasp. Cf. Auf, Oaf.]
   1. An imaginary supernatural being, commonly a little sprite,
      much like a fairy; a mythological diminutive spirit,
      supposed to haunt hills and wild places, and generally
      represented as delighting in mischievous tricks.
      [1913 Webster]

            Every elf, and fairy sprite,
            Hop as light as bird from brier.      --Shak.
      [1913 Webster]

   2. A very diminutive person; a dwarf.
      [1913 Webster]

   Elf arrow, a flint arrowhead; -- so called by the English
      rural folk who often find these objects of prehistoric
      make in the fields and formerly attributed them to
      fairies; -- called also elf bolt, elf dart, and elf
      shot.

   Elf child, a child supposed to be left by elves, in room of
      one they had stolen. See Changeling.

   Elf fire, the ignis fatuus. --Brewer.

   Elf owl (Zo["o]l.), a small owl (Micrathene Whitneyi) of
      Southern California and Arizona.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Elf \Elf\, v. t.
   To entangle mischievously, as an elf might do.
   [1913 Webster]

         Elf all my hair in knots.                --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

elf
    n 1: (folklore) fairies that are somewhat mischievous [syn:
         elf, hob, gremlin, pixie, pixy, brownie, imp]
    2: below 3 kilohertz [syn: extremely low frequency, ELF]

Moby Thesaurus II by Grady Ward, 1.0:

97 Moby Thesaurus words for "elf":
   Ariel, Befind, Corrigan, Dingbelle, Fifinella, Finnbeara, Hob,
   Hobgoblin, JD, Lilliputian, Mab, Oberon, Puck, Titania, Tom Thumb,
   bad boy, bad fairy, bad peri, banshee, booger, brat, brownie,
   buffoon, bugger, cluricaune, cutup, devil, deviling, devilkin,
   diablotin, dwarf, enfant terrible, erlking, fairy, fairy queen,
   fay, funmaker, gamin, gnome, goblin, gremlin, hob, holy terror,
   homunculus, hood, hoodlum, hooligan, imp, joker, jokester,
   juvenile delinquent, knave, kobold, leprechaun, little devil,
   little monkey, little rascal, manikin, midge, midget, minx,
   mischief, mischief-maker, ouphe, peewee, peri, pip-squeak, pixie,
   poltergeist, pooka, practical joker, prankster, puca, puck, punk,
   punk kid, pwca, pygmy, rapscallion, rascal, rogue, rowdy, ruffian,
   runt, scamp, scapegrace, shrimp, spoiled brat, sprite, sylph,
   sylphid, tokoloshe, urchin, wag, wart, whippersnapper,
   young devil



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

ELF
       Executable and Linkable Format (Unix, OS/2)


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

ELF

   Binary format used by System V Release 4 Unix.