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):

knowledgeable
    adj 1: highly educated; having extensive information or
           understanding; "knowing instructors"; "a knowledgeable
           critic"; "a knowledgeable audience" [syn: knowing,
           knowledgeable, learned, lettered, well-educated,
           well-read]
    2: alert and fully informed; "a knowing collector of rare
       books"; "surprisingly knowledgeable about what was going on"
       [syn: knowledgeable, knowing]
    3: thoroughly acquainted through study or experience; "this
       girl, so intimate with nature"-W.H.Hudson; "knowledgeable
       about the technique of painting"- Herbert Read [syn:
       intimate, knowledgeable, versed]