Source : Webster's Revised Unabridged Dictionary (1913)

Lip \Lip\ (l[i^]p), n. [OE. lippe, AS. lippa; akin to D. lip, G.
   lippe, lefze, OHG. lefs, Dan. l[ae]be, Sw. l["a]pp, L.
   labium, labrum. Cf. {Labial}.]
   1. One of the two fleshy folds which surround the orifice of
      the mouth in man and many other animals. In man the lips
      are organs of speech essential to certain articulations.
      Hence, by a figure they denote the mouth, or all the
      organs of speech, and sometimes speech itself.

            Thine own lips testify against thee.  --Job xv. 6.

   2. An edge of an opening; a thin projecting part of anything;
      a kind of short open spout; as, the lip of a vessel.

   3. The sharp cutting edge on the end of an auger.

   4. (Bot.)
      (a) One of the two opposite divisions of a labiate
          corolla. (b) The odd and peculiar petal in the
          {Orchis} family. See {Orchidaceous}.

   5. (Zo["o]l.) One of the edges of the aperture of a univalve
      shell.

   {Lip bit}, a pod auger. See {Auger}.

   {Lip comfort}, comfort that is given with words only.

   {Lip comforter}, one who comforts with words only.

   {Lip labor}, unfelt or insincere speech; hypocrisy. --Bale.

   {Lip reading}, the catching of the words or meaning of one
      speaking by watching the motion of his lips without
      hearing his voice. --Carpenter.

   {Lip salve}, a salve for sore lips.

   {Lip service}, expression by the lips of obedience and
      devotion without the performance of acts suitable to such
      sentiments.

   {Lip wisdom}, wise talk without practice, or unsupported by
      experience.

   {Lip work}.
      (a) Talk.
      (b) Kissing. [Humorous] --B. Jonson.

   {To make a lip}, to drop the under lip in sullenness or
      contempt. --Shak.

   {To shoot out the lip} (Script.), to show contempt by
      protruding the lip.

Source : WordNet®

lip service
     n : an expression of agreement that is not supported by real
         conviction [syn: {hypocrisy}]