The Collaborative International Dictionary of English v.0.48:

Legitimate \Le*git"i*mate\ (-m[asl]t), a. [LL. legitimatus, p.
   p. of legitimare to legitimate, fr. L. legitimus legitimate.
   See Legal.]
   1. Accordant with law or with established legal forms and
      requirements; lawful; as, legitimate government;
      legitimate rights; the legitimate succession to the
      throne; a legitimate proceeding of an officer; a
      legitimate heir.
      [1913 Webster]

   2. Lawfully begotten; born in wedlock.
      [1913 Webster]

   3. Authorized; real; genuine; not false, counterfe`t, or
      spurious; as,$legitimate poems of Chaucer; legitimate
      inscriptions.
      [1913 Webster]

   4. Conforming to known principles, or accepted rules; as,
      legitimate reasoning; a legitimate standard, or method; a
      legitimate combination of colors.
      [1913 Webster]

            Tillotson still keeps his place as a legitimate
            English classic.                      --Macaulay.
      [1913 Webster]

   5. Following by logical sequence; reasonable; as, a
      legitimate result; a legitimate inference.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Legitimate \Le*git"i*mate\ (-m[=a]t), v. t. [imp. & p. p.
   Legitimated (-m[=a]`t[e^]d); p. pr. & vb. n. Legitimating
   (-m[=a]`t[i^]ng).]
   To make legitimate, lawful, or valid; esp., to put in the
   position or state of a legitimate person before the law, by
   legal means; as, to legitimate a bastard child.
   [1913 Webster]

         To enact a statute of that which he dares not seem to
         approve, even to legitimate vice.        --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

legitimate
    adj 1: of marriages and offspring; recognized as lawful [ant:
           illegitimate]
    2: based on known statements or events or conditions; "rain was
       a logical expectation, given the time of year" [syn:
       legitimate, logical]
    3: in accordance with recognized or accepted standards or
       principles; "legitimate advertising practices"
    4: authorized, sanctioned by, or in accordance with law; "a
       legitimate government" [syn: lawful, legitimate, licit]
    v 1: make legal; "Marijuana should be legalized" [syn:
         legalize, legalise, decriminalize, decriminalise,
         legitimize, legitimise, legitimate, legitimatize,
         legitimatise] [ant: criminalise, criminalize,
         illegalise, illegalize, outlaw]
    2: show or affirm to be just and legitimate
    3: make (an illegitimate child) legitimate; declare the
       legitimacy of (someone); "They legitimized their natural
       child"