The Collaborative International Dictionary of English v.0.48:

Plenteous \Plen"te*ous\, a. [From Plenty.]
   1. Containing plenty; abundant; copious; plentiful;
      sufficient for every purpose; as, a plenteous supply.
      "Reaping plenteous crop." --Milton.
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   2. Yielding abundance; productive; fruitful. "The seven
      plenteous years." --Gen. xli. 34.
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   3. Having plenty; abounding; rich.
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            The Lord shall make thee plenteous in goods. --Deut.
                                                  xxviii. 11.
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   Syn: Plentiful; copious; full. See Ample.
        [1913 Webster] -- Plen"te*ous*ly, adv. --
        Plen"te*ous*ness, n.
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WordNet (r) 3.0 (2006):

plenteously
    adv 1: in a bountiful manner [syn: bountifully, bounteously,
           plentifully, plenteously]