The Collaborative International Dictionary of English v.0.48:

knowledgeable \knowledgeable\ adj.
   1. thoroughly acquainted with and skilled in something
      through study or experience; as, knowledgeable in
      classical languages. Opposite of unversed,
      unacquainted, and unfamiliar.

   Syn: versed.
        [WordNet 1.5]

   2. fully informed.
      [WordNet 1.5]

   3. highly educated; having information or understanding.

   Syn: enlightened, learned, lettered, literate, well-educated,
        well-read.
        [WordNet 1.5] -- knowledgeability, n. --
        knowledgeably, adv. -- knowledgeableness, n.
        [PJC]

WordNet (r) 3.0 (2006):

knowledgeableness
    n 1: wisdom as evidenced by the possession of knowledge; "his
         knowledgeability impressed me"; "his dullness was due to
         lack of initiation" [syn: knowledgeability,
         knowledgeableness, initiation]