The Collaborative International Dictionary of English v.0.48:

Earmark \Ear"mark`\ ([=e]r"m[aum]rk`), n.
   1. A mark on the ear of sheep, oxen, dogs, etc., as by
      cropping or slitting.
      [1913 Webster]

   2. A mark for identification; a distinguishing mark.
      [1913 Webster]

            Money is said to have no earmark.     --Wharton.
      [1913 Webster]

            Flying, he [a slave] should be described by the
            rounding of his head, and his earmark. --Robynson
                                                  (More's
                                                  Utopia).
      [1913 Webster]

            A set of intellectual ideas . . . have earmarks upon
            them, no tokens of a particular proprietor.
                                                  --Burrow.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Earmark \Ear"mark`\, v. t. [imp. & p. p. Earmarked; p. pr. &
   vb. n. Earmarking.]
   1. To mark, as sheep, by cropping or slitting the ear.
      [1913 Webster]

   2. To designate or reserve for a specific purpose; as, the
      alumni fund was earmarked for dormitory construction.
      [PJC]

WordNet (r) 3.0 (2006):

earmark
    n 1: identification mark on the ear of a domestic animal
    2: a distinctive characteristic or attribute [syn: hallmark,
       trademark, earmark, stylemark]
    v 1: give or assign a resource to a particular person or cause;
         "I will earmark this money for your research"; "She sets
         aside time for meditation every day" [syn: allow,
         appropriate, earmark, set aside, reserve]

Moby Thesaurus II by Grady Ward, 1.0:

156 Moby Thesaurus words for "earmark":
   allocate, allot, appoint, appropriate to, aroma, assign, assign to,
   attribute, badge, banner, be characteristic, birthmark, blaze,
   blemish, blotch, brand, cachet, cast, caste mark, character,
   characteristic, characterize, check, checkmark, cicatrix,
   configuration, cut, dapple, define, demarcate, describe, destine,
   detail, device, differentia, differential, differentiate,
   discoloration, distinctive feature, distinguish, dot, engraving,
   fate, feature, figure, flavor, fleck, flick, freckle, gash,
   graving, gust, hack, hallmark, idiocrasy, idiosyncrasy, image,
   impress, impression, index, indicant, indicator, individualism,
   insignia, jot, keynote, label, lentigo, lineaments, lot, macula,
   make assignments, mannerism, mark, mark off, mark out,
   mark out for, marking, measure, mold, mole, mottle, nature, nevus,
   nick, notch, note, odor, ordain, particularity, patch, peculiarity,
   picture, point, polka dot, portion off, prick, property, puncture,
   quality, quirk, representation, representative, reserve, restrict,
   restrict to, savor, scar, scarification, schedule, score, scotch,
   scratch, scratching, seal, set, set apart, set aside, set off,
   set the pace, set the tone, shape, sigil, sign, signal, signature,
   singularity, smack, sound the keynote, specialty, speck, speckle,
   splash, splotch, spot, stain, stamp, stigma, strawberry mark,
   sure sign, symptom, tab, tag, taint, tang, taste, tattoo,
   tattoo mark, telltale sign, tick, ticket, tittle, token, trait,
   trick, watermark