[syn: pronounce, label, judge]
4.  distinguish (as a compound or molecule) by introducing a labeled atom; 
5.  distinguish (an element or atom) by using a radioactive isotope or an isotope of unusual mass for tracing through chemical reactions; 
The Collaborative International Dictionary of English v.0.48:
Label \La"bel\, v. t. [imp. & p. p. Labeled (l[=a]"b[e^]ld) or
   Labelled; p. pr. & vb. n. Labeling or Labelling.]
   1. To affix a label to; to mark with a name, etc.; as, to
      label a bottle or a package.
      [1913 Webster]
   2. To affix in or on a label. [R.]
      [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Label \La"bel\ (l[=a]"b[e^]l), n. [OF. label sort of ribbon or
   fringe, label in heraldry, F. lambeau shred, strip, rag; of
   uncertain origin; cf. L. labellum, dim. of labrum lip, edge,
   margin, G. lappen flap, patch, rag, tatter (cf. Lap of a
   dress), W. llab, llabed, label, flap, Gael. leab, leob,
   slice, shred, hanging lip.]
   1. A tassel. [Obs.] --Huloet. --Fuller.
      [1913 Webster]
   2. A slip of silk, paper, parchment, etc., affixed to
      anything, and indicating, usually by an inscription, the
      contents, ownership, destination, etc.; as, the label of a
      bottle or a package.
      [1913 Webster]
   3. A slip of ribbon, parchment, etc., attached to a document
      to hold the appended seal; also, the seal.
      [1913 Webster]
   4. A writing annexed by way of addition, as a codicil added
      to a will.
      [1913 Webster]
   5. (Her.) A barrulet, or, rarely, a bendlet, with pendants,
      or points, usually three, especially used as a mark of
      cadency to distinguish an eldest or only son while his
      father is still living.
      [1913 Webster]
   6. A brass rule with sights, formerly used, in connection
      with a circumferentor, to take altitudes. --Knight.
      [1913 Webster]
   7. (Gothic Arch.) The name now generally given to the
      projecting molding by the sides, and over the tops, of
      openings in medi[ae]val architecture. It always has a
      square form, as in the illustration. --Arch. Pub. Soc.
      [1913 Webster]
   8. In medi[ae]val art, the representation of a band or scroll
      containing an inscription. --Fairholt.
      [1913 Webster]
WordNet (r) 3.0 (2006):
label
    n 1: a brief description given for purposes of identification;
         "the label Modern is applied to many different kinds of
         architecture"
    2: trade name of a company that produces musical recordings;
       "the artists and repertoire department of a recording label
       is responsible for finding new talent" [syn: label,
       recording label]
    3: a radioactive isotope that is used in a compound in order to
       trace the mechanism of a chemical reaction
    4: an identifying or descriptive marker that is attached to an
       object
    v 1: assign a label to; designate with a label; "These students
         were labelled `learning disabled'"
    2: attach a tag or label to; "label these bottles" [syn: tag,
       label, mark]
    3: pronounce judgment on; "They labeled him unfit to work here"
       [syn: pronounce, label, judge]
    4: distinguish (as a compound or molecule) by introducing a
       labeled atom
    5: distinguish (an element or atom) by using a radioactive
       isotope or an isotope of unusual mass for tracing through
       chemical reactions
Moby Thesaurus II by Grady Ward, 1.0:
262 Moby Thesaurus words for "label":
   achievement, alerion, animal charge, annulet, appellation,
   appellative, argent, armorial bearings, armory, arms, azure,
   bandeau, baptize, bar, bar sinister, baton, bearings, bend,
   bend sinister, billet, billhead, binomen, binomial name, blazon,
   blazonry, blood, book stamp, bookplate, bordure, bracket, branch,
   brand, breed, broad arrow, byword, cachet, cadency mark, call,
   canton, cast, caste, categorize, category, chaplet, character,
   characterization, characterize, charge, check, chevron, chief,
   christen, clan, class, classification, classify, coat of arms,
   cockatrice, cognomen, colophon, color, coronet, counterfoil,
   countermark, crescent, crest, cross, cross moline, crown,
   cryptonym, define, denominate, denomination, describe, description,
   designate, designation, device, difference, differencing, division,
   docket, dub, eagle, earmark, empty title, entitle, epithet, eponym,
   ermine, ermines, erminites, erminois, escutcheon, estate, euonym,
   falcon, feather, fess, fess point, field, file, flanch,
   fleur-de-lis, form, fret, fur, fusil, garland, genre, genus,
   government mark, government stamp, grade, grain, griffin, group,
   grouping, gules, gyron, hallmark, handle, hatchment, head, heading,
   helmet, heraldic device, honor point, honorific, hyponym,
   identification, identifier, identify, ilk, impalement, impaling,
   imprint, inescutcheon, kidney, kin, kind, letterhead, level, line,
   lion, logo, logotype, lot, lozenge, make, manner, mantling, mark,
   marker, marshaling, martlet, mascle, masthead, metal, mold,
   moniker, motto, mullet, name, namesake, nature, nickname,
   nombril point, nomen, nomen nudum, nominate, number, octofoil, or,
   order, ordinary, orle, pale, paly, pean, peg, persuasion, pheon,
   phylum, pigeonhole, plate, portray, position, predicament,
   price tag, proper name, proper noun, purpure, quarter, quartering,
   race, rank, rating, registered trademark, rose, rubric,
   running head, running title, sable, saltire, scientific name,
   scutcheon, seal, secret name, section, sept, set, shape, shield,
   sigil, signet, sobriquet, sort, species, specify, spread eagle,
   stamp, station, status, sticker, strain, stratum, stripe, stub,
   style, subdivision, subgroup, suborder, subordinary, tab, tag,
   tally, tautonym, tenne, term, the like of, the likes of, ticket,
   tincture, title, title page, token, torse, trade name, trademark,
   trademark name, tressure, tribe, trinomen, trinomial name, type,
   unicorn, vair, variety, vert, wreath, yale
The Free On-line Dictionary of Computing (30 December 2018):
label
   1.  An identifier used to mark a position in a
   program so that it can be the destination of a goto
   statement.
   2.  The identifier assigned to a datagram for
   label switching.
   (2007-10-17)
Bouvier's Law Dictionary, Revised 6th Ed (1856):
LABEL. A narrow slip of paper or parchment, affixed to a deed or writing
hanging at or out of the same. This name is also given to an appending seal.