Source : Webster's Revised Unabridged Dictionary (1913)

Sermon \Ser"mon\, n. [OE. sermoun, sermun, F. sermon, fr. L.
   sermo, -onis, a speaking, discourse, probably fr. serer,
   sertum, to join, connect; hence, a connected speech. See
   {Series}.]
   1. A discourse or address; a talk; a writing; as, the sermons
      of Chaucer. [Obs.] --Chaucer.

   2. Specifically, a discourse delivered in public, usually by
      a clergyman, for the purpose of religious instruction and
      grounded on some text or passage of Scripture.

            This our life exempt from public haunts Finds
            tongues in trees, books in the running brooks,
            Sermons in stones and good in everything. --Shak.

            His preaching much, but more his practice, wrought,
            A living sermon of the truths he taught. --Dryden.

   3. Hence, a serious address; a lecture on one's conduct or
      duty; an exhortation or reproof; a homily; -- often in a
      depreciatory sense.

Sermon \Ser"mon\, v. i. [Cf. OF. sermoner, F. sermonner to
   lecture one.]
   To speak; to discourse; to compose or deliver a sermon.
   [Obs.] --Holinshed.

         What needeth it to sermon of it more?    --Chaucer.

Sermon \Ser"mon\, v. t.
   1. To discourse to or of, as in a sermon. [Obs.] --Spenser.

   2. To tutor; to lecture. [Poetic] --Shak.

Source : WordNet®

sermon
     n 1: an address of a religious nature (usually delivered during a
          church service) [syn: {discourse}, {preaching}]
     2: a moralistic rebuke; "your preaching is wasted on him" [syn:
         {preaching}]