The Collaborative International Dictionary of English v.0.48:

Illegitimation \Il`le*git`i*ma"tion\, n.
   1. The act of illegitimating; bastardizing.
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   2. The state of being illegitimate; illegitimacy. [Obs.]
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            Gardiner had performed his promise to the queen of
            getting her illegitimation taken off. --Bp. Burnet.
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