The Collaborative International Dictionary of English v.0.48:

Sappy \Sap"py\, a. [Compar. Sappier; superl. Sappiest.]
   [From 1st Sap.]
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   1. Abounding with sap; full of sap; juicy; succulent.
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   2. Hence, young, not firm; weak, feeble.
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            When he had passed this weak and sappy age.
                                                  --Hayward.
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   3. Weak in intellect. [Low]
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   4. (Bot.) Abounding in sap; resembling, or consisting largely
      of, sapwood.
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