The Collaborative International Dictionary of English v.0.48:

Know \Know\ (n[=o]), v. t. [imp. Knew (n[=u]); p. p. Known
   (n[=o]n); p. pr. & vb. n. Knowing.] [OE. knowen, knawen,
   AS. cn[aum]wan; akin to OHG. chn[aum]an (in comp.), Icel.
   kn[aum] to be able, Russ. znate to know, L. gnoscere,
   noscere, Gr. gighw`skein, Skr. jn[=a]; fr. the root of E.
   can, v. i., ken. [root]45. See Ken, Can to be able, and
   cf. Acquaint, Cognition, Gnome, Ignore, Noble,
   Note.]
   1. To perceive or apprehend clearly and certainly; to
      understand; to have full information of; as, to know one's
      duty.
      [1913 Webster]

            O, that a man might know
            The end of this day's business ere it come! --Shak.
      [1913 Webster]

            There is a certainty in the proposition, and we know
            it.                                   --Dryden.
      [1913 Webster]

            Know how sublime a thing it is
            To suffer and be strong.              --Longfellow.
      [1913 Webster]

   2. To be convinced of the truth of; to be fully assured of;
      as, to know things from information.
      [1913 Webster]

   3. To be acquainted with; to be no stranger to; to be more or
      less familiar with the person, character, etc., of; to
      possess experience of; as, to know an author; to know the
      rules of an organization.
      [1913 Webster]

            He hath made him to be sin for us, who knew no sin.
                                                  --2 Cor. v.
                                                  21.
      [1913 Webster]

            Not to know me argues yourselves unknown. --Milton.
      [1913 Webster]

   4. To recognize; to distinguish; to discern the character of;
      as, to know a person's face or figure.
      [1913 Webster]

            Ye shall know them by their fruits.   --Matt. vil.
                                                  16.
      [1913 Webster]

            And their eyes were opened, and they knew him.
                                                  --Luke xxiv.
                                                  31.
      [1913 Webster]

            To know
            Faithful friend from flattering foe.  --Shak.
      [1913 Webster]

            At nearer view he thought he knew the dead.
                                                  --Flatman.
      [1913 Webster]

   5. To have sexual intercourse with.
      [1913 Webster]

            And Adam knew Eve his wife.           --Gen. iv. 1.
      [1913 Webster]

   Note: Know is often followed by an objective and an
         infinitive (with or without to) or a participle, a
         dependent sentence, etc.
         [1913 Webster]

               And I knew that thou hearest me always. --John
                                                  xi. 42.
         [1913 Webster]

               The monk he instantly knew to be the prior. --Sir
                                                  W. Scott.
         [1913 Webster]

               In other hands I have known money do good.
                                                  --Dickens.
         [1913 Webster]

   To know how, to understand the manner, way, or means; to
      have requisite information, intelligence, or sagacity. How
      is sometimes omitted. " If we fear to die, or know not to
      be patient." --Jer. Taylor.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Known \Known\, p. p.
   of Know.
   [1913 Webster]

WordNet (r) 3.0 (2006):

known
    adj 1: apprehended with certainty; "a known quantity"; "the
           limits of the known world"; "a musician known throughout
           the world"; "a known criminal" [ant: unknown]