The Collaborative International Dictionary of English v.0.48:

Betrap \Be*trap"\, v. t. [imp. & p. p. Betrapped.]
   1. To draw into, or catch in, a trap; to insnare; to
      circumvent. --Gower.
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   2. To put trappings on; to clothe; to deck.
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            After them followed two other chariots covered with
            red satin, and the horses betrapped with the same.
                                                  --Stow.
      [1913 Webster]