\Un*rea"son\, n. [Pref. un- not + reason.]
Want of reason; unreasonableness; absurdity.
{Abbot of Unreason}. See {Abbot of Misrule}, under {Abbot}.

\Un*rea"son\, v. t. [1st pref. un- + reason.]
To undo, disprove, or refute by reasoning. [Obs.]
      To unreason the equity of God's proceedings. --South.