The Collaborative International Dictionary of English v.0.48:

Sermonize \Ser"mon*ize\, v. t.
   To preach or discourse to; to affect or influence by means of
   a sermon or of sermons. [R.]
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         Which of us shall sing or sermonize the other fast
         asleep?                                  --Landor.
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The Collaborative International Dictionary of English v.0.48:

Sermonize \Ser"mon*ize\, v. i. [imp. & p. p. Sermonized; p.
   pr. & vb. n. Sermonizing.]
   1. To compose or write a sermon or sermons; to preach.
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   2. To inculcate rigid rules. [R.] --Chesterfield.
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WordNet (r) 3.0 (2006):

sermonize
    v 1: speak as if delivering a sermon; express moral judgements;
         "This man always sermonizes" [syn: sermonize,
         sermonise, preachify, moralize, moralise]