The Collaborative International Dictionary of English v.0.48:

Officiate \Of*fi"ci*ate\, v. i. [imp. & p. p. Officiated; p.
   pr. & vb. n. Officiating.] [LL. officiare. See Office.]
   To act as an officer in performing a duty; to transact the
   business of an office or public trust; to conduct a public
   ceremony or service. --Bp. Stillingfleet.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Officiate \Of*fi"ci*ate\, v. t.
   To discharge, perform, or supply, as an official duty or
   function. [Obs.]
   [1913 Webster]

         Merely to officiate light
         Round this opacous earth.                --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

officiate
    v 1: act in an official capacity in a ceremony or religious
         ritual, such as a wedding; "Who officiated at your
         wedding?"
    2: perform duties attached to a particular office or place or
       function; "His wife officiated as his private secretary"
       [syn: officiate, function]