The Collaborative International Dictionary of English v.0.48:

Instead \In*stead"\, adv. [Pref. in- + stead place.]
   [1913 Webster]
   1. In the place or room; -- usually followed by of.
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            Let thistles grow of wheat.           --Job xxxi.
                                                  40.
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            Absalom made Amasa captain of the host instead of
            Joab.                                 --2 Sam. xvii.
                                                  25.
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   2. Equivalent; equal to; -- usually with of. [R.]
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            This very consideration to a wise man is instead of
            a thousand arguments, to satisfy him, that in those
            times no such thing was believed.     --Tillotson.
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WordNet (r) 3.0 (2006):

instead
    adv 1: in place of, or as an alternative to; "Felix became a
           herpetologist instead"; "alternatively we could buy a
           used car" [syn: alternatively, instead, or else]
    2: on the contrary; "rather than disappoint the children, he did
       two quick tricks before he left"; "he didn't call; rather (or
       instead), he wrote her a letter"; "used English terms instead
       of Latin ones" [syn: rather, instead]