The Collaborative International Dictionary of English v.0.48:

Excommunicate \Ex`com*mu"ni*cate\, v. t. [imp. & p. p.
   Excommunicated; p. pr. & vb. n. Excommunicating.]
   1. To put out of communion; especially, to cut off, or shut
      out, from communion with the church, by an ecclesiastical
      sentence.
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   2. To lay under the ban of the church; to interdict.
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            Martin the Fifth . . . was the first that
            excommunicated the reading of heretical books.
                                                  --Miltin.
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