The Collaborative International Dictionary of English v.0.48:

Weighty \Weight"y\, a. [Compar. Weightier; superl.
   Weightiest.]
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   1. Having weight; heavy; ponderous; as, a weighty body.
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   2. Adapted to turn the balance in the mind, or to convince;
      important; forcible; serious; momentous. "For sundry
      weighty reasons." --Shak.
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            Let me have your advice in a weighty affair.
                                                  --Swift.
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   3. Rigorous; severe; afflictive. [R.] "Attend our weightier
      judgment." --Shak.
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   Syn: Heavy; ponderous; burdensome; onerous; forcible;
        momentous; efficacious; impressive; cogent.
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