The Collaborative International Dictionary of English v.0.48:

Bethink \Be*think"\, v. t. [imp. & p. p. Bethought; p. pr. &
   vb. n. Bethinking.] [AS. be[thorn]encan; pref. be- +
   [thorn]encan to think. See Think.]
   To call to mind; to recall or bring to recollection,
   reflection, or consideration; to think; to consider; --
   generally followed by a reflexive pronoun, often with of or
   that before the subject of thought.
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         I have bethought me of another fault.    --Shak.
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         The rest . . . may . . . bethink themselves, and
         recover.                                 --Milton.
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         We bethink a means to break it off.      --Shak.
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   Syn: To recollect; remember; reflect.
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The Collaborative International Dictionary of English v.0.48:

Bethink \Be*think"\, v. i.
   To think; to recollect; to consider. "Bethink ere thou
   dismiss us." --Byron.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bethink
    v 1: cause oneself to consider something
    2: consider or ponder something carefully; "She bethought her of
       their predicament"