Source : Webster's Revised Unabridged Dictionary (1913)

Cynic \Cyn"ic\, n. (Gr. Philos)
   1. One of a sect or school of philosophers founded by
      Antisthenes, and of whom Diogenes was a disciple. The
      first Cynics were noted for austere lives and their scorn
      for social customs and current philosophical opinions.
      Hence the term Cynic symbolized, in the popular judgment,
      moroseness, and contempt for the views of others.

   2. One who holds views resembling those of the Cynics; a
      snarler; a misanthrope; particularly, a person who
      believes that human conduct is directed, either
      consciously or unconsciously, wholly by self-interest or
      self-indulgence, and that appearances to the contrary are
      superficial and untrustworthy.

            He could obtain from one morose cynic, whose opinion
            it was impossible to despise, scarcely any not
            acidulated with scorn.                --Macaulay.

Cynic \Cyn"ic\ (s[i^]n"[i^]k), Cynical \Cyn"ic*al\ (-[i^]*kal),
   a. [L. cynicus of the sect of Cynics, fr. Gr. kyniko`s,
   prop., dog-like, fr. ky`wn, kyno`s, dog. See {Hound}.]
   1. Having the qualities of a surly dog; snarling; captious;
      currish.

            I hope it is no very cynical asperity not to confess
            obligations where no benefit has been received.
                                                  --Johnson.

   2. Pertaining to the Dog Star; as, the cynic, or Sothic,
      year; cynic cycle.

   3. Belonging to the sect of philosophers called cynics;
      having the qualities of a cynic; pertaining to, or
      resembling, the doctrines of the cynics.

   4. Given to sneering at rectitude and the conduct of life by
      moral principles; disbelieving in the reality of any human
      purposes which are not suggested or directed by
      self-interest or self-indulgence; as, a cynical man who
      scoffs at pretensions of integrity; characterized by such
      opinions; as, cynical views of human nature.

   Note: In prose, cynical is used rather than cynic, in the
         senses 1 and 4.

   {Cynic spasm} (Med.), a convulsive contraction of the muscles
      of one side of the face, producing a sort of grin,
      suggesting certain movements in the upper lip of a dog.

Source : WordNet®

cynic
     n 1: someone who is critical of the motives of others [syn: {faultfinder}]
     2: a member of a group of ancient Greek philosophers who
        advocated the doctrine that virtue is the only good and
        that the essence of virtue is self-control