The Collaborative International Dictionary of English v.0.48:

Tag \Tag\, n. [From Tag, v.; cf. Tag, an end.]
   A child's play in which one runs after and touches another,
   and then runs away to avoid being touched.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tag \Tag\, n. [Probably akin to tack a small nail; cf. Sw. tagg
   a prickle, point, tooth.]
   1. Any slight appendage, as to an article of dress; something
      slight hanging loosely; specifically, a direction card, or
      label.
      [1913 Webster]

   2. A metallic binding, tube, or point, at the end of a
      string, or lace, to stiffen it.
      [1913 Webster]

   3. The end, or catchword, of an actor's speech; cue.
      [1913 Webster]

   4. Something mean and paltry; the rabble. [Obs.]
      [1913 Webster]

   Tag and rag, the lowest sort; the rabble. --Holinshed.
      [1913 Webster]

   5. A sheep of the first year. [Prov. Eng.] --Halliwell.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tag \Tag\, v. t. [imp. & p. p. Tagged; p. pr. & vb. n.
   Tagging.]
   1. To fit with, or as with, a tag or tags.
      [1913 Webster]

            He learned to make long-tagged thread laces.
                                                  --Macaulay.
      [1913 Webster]

            His courteous host . . .
            Tags every sentence with some fawning word.
                                                  --Dryden.
      [1913 Webster]

   2. To join; to fasten; to attach. --Bolingbroke.
      [1913 Webster]

   3. To follow closely after; esp., to follow and touch in the
      game of tag. See Tag, a play.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tag \Tag\, v. i.
   To follow closely, as it were an appendage; -- often with
   after; as, to tag after a person.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tag
    n 1: a label written or printed on paper, cardboard, or plastic
         that is attached to something to indicate its owner,
         nature, price, etc. [syn: tag, ticket]
    2: a label associated with something for the purpose of
       identification; "semantic tags were attached in order to
       identify different meanings of the word"
    3: a small piece of cloth or paper [syn: rag, shred, tag,
       tag end, tatter]
    4: a game in which one child chases the others; the one who is
       caught becomes the next chaser
    5: (sports) the act of touching a player in a game (which
       changes their status in the game)
    v 1: attach a tag or label to; "label these bottles" [syn:
         tag, label, mark]
    2: touch a player while he is holding the ball
    3: provide with a name or nickname
    4: go after with the intent to catch; "The policeman chased the
       mugger down the alley"; "the dog chased the rabbit" [syn:
       chase, chase after, trail, tail, tag, give chase,
       dog, go after, track]
    5: supply (blank verse or prose) with rhymes

The Free On-line Dictionary of Computing (19 January 2023):

tag
empty element tag
end tag
start tag

    An SGML, HTML, or XML token
   representing the beginning (start tag: "
") or end (end
   tag: "
") of an element.  In normal SGML syntax (and
   always in XML), a tag starts with a "<" and ends with an
   ">".

   In HTML jargon, the term "tag" is often used for an
   "element".

   (2001-01-31)