The Collaborative International Dictionary of English v.0.48:

Pithy \Pith"y\, a. [Compar. Pithier; superl. Pithiest.]
   1. Consisting wholly, or in part, of pith; abounding in pith;
      as, a pithy stem; a pithy fruit.
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   2. Having nervous energy; forceful; cogent.
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            This pithy speech prevailed, and all agreed.
                                                  --Dryden.
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            In all these Goodman Fact was very short, but pithy.
                                                  --Addison.
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   Pithy gall (Zool.), a large, rough, furrowed, oblong gall,
      formed on blackberry canes by a small gallfly
      (Diastrophus nebulosus).
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WordNet (r) 3.0 (2006):

pithy
    adj 1: concise and full of meaning; "welcomed her pithy
           comments"; "the peculiarly sardonic and sententious style
           in which Don Luis composed his epigrams"- Hervey Allen
           [syn: pithy, sententious]