The Collaborative International Dictionary of English v.0.48:

Godhead \God"head\, n. [OE. godhed. See -head, and cf.
   Godhood.]
   1. Godship; deity; divinity; divine nature or essence;
      godhood.
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   2. The Deity; God; the Supreme Being.
      [1913 Webster]

            The imperial throne
            Of Godhead, fixed for ever.           --Milton.
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   3. A god or goddess; a divinity. [Obs.]
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            Adoring first the genius of the place,
            The nymphs and native godheads yet unknown.
                                                  --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Godhead
    n 1: terms referring to the Judeo-Christian God [syn: Godhead,
         Lord, Creator, Maker, Divine, God Almighty,
         Almighty, Jehovah]

Easton's 1897 Bible Dictionary:

Godhead
   (Acts 17:29; Rom. 1:20; Col. 2:9), the essential being or the
   nature of God.