Source : Webster's Revised Unabridged Dictionary (1913)

Topic \Top"ic\, n. [F. topiques, pl., L. topica the title of a
   work of Aristotle, Gr. topika`, fr. topiko`s of or for place,
   concerning to`poi, or commonplaces, fr. to`pos a place.]
   (a) One of the various general forms of argument employed in
       probable as distinguished from demonstrative reasoning,
       -- denominated by Aristotle to`poi (literally, places),
       as being the places or sources from which arguments may
       be derived, or to which they may be referred; also, a
       prepared form of argument, applicable to a great variety
       of cases, with a supply of which the ancient rhetoricians
       and orators provided themselves; a commonplace of
       argument or oratory.
   (b) pl. A treatise on forms of argument; a system or scheme
       of forms or commonplaces of argument or oratory; as, the
       Topics of Aristotle.

             These topics, or loci, were no other than general
             ideas applicable to a great many different
             subjects, which the orator was directed to consult.
                                                  --Blair.

             In this question by [reason] I do not mean a
             distinct topic, but a transcendent that runs
             through all topics.                  --Jer. Taylor.

   2. An argument or reason. [Obs.]

            Contumacious persons, who are not to be fixed by any
            principles, whom no topics can work upon. --Bp.
                                                  Wilkins.

   3. The subject of any distinct portion of a discourse, or
      argument, or literary composition; also, the general or
      main subject of the whole; a matter treated of; a subject,
      as of conversation or of thought; a matter; a point; a
      head.

   4. (Med.) An external local application or remedy, as a
      plaster, a blister, etc. [Obsoles.] --Wiseman.

Topic \Top"ic\, a.
   Topical. --Drayton. Holland.

Source : WordNet®

topic
     n 1: the subject matter of a conversation or discussion; "he
          didn't want to discuss that subject"; "it was a very
          sensitive topic"; "his letters were always on the theme
          of love" [syn: {subject}, {theme}]
     2: some situation or event that is thought about; "he kept
        drifting off the topic"; "he had been thinking about the
        subject for several years"; "it is a matter for the
        police" [syn: {subject}, {issue}, {matter}]