The Collaborative International Dictionary of English v.0.48:

Welcome \Wel"come\, v. t. [imp. & p. p. Welcomed; p. pr. & vb.
   n. Welcoming.] [AS. wilcumian.]
   To salute with kindness, as a newcomer; to receive and
   entertain hospitably and cheerfully; as, to welcome a
   visitor; to welcome a new idea. "I welcome you to land."
   --Addison.
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         Thus we salute thee with our early song,
         And welcome thee, and wish thee long.    --Milton.
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The Collaborative International Dictionary of English v.0.48:

Welcome \Wel"come\, a. [OE. welcome, welcume, wilcume, AS.
   wilcuma a welcome guest, from wil-, as a prefix, akin to
   willa will + cuma a comer, fr. cuman to come; hence,
   properly, one who comes so as to please another's will; cf.
   Icel. velkominn welcome, G. willkommen. See Will, n., and
   Come.]
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   1. Received with gladness; admitted willingly to the house,
      entertainment, or company; as, a welcome visitor.
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            When the glad soul is made Heaven's welcome guest.
                                                  --Cowper.
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   2. Producing gladness; grateful; as, a welcome present;
      welcome news. "O, welcome hour!" --Milton.
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   3. Free to have or enjoy gratuitously; as, you are welcome to
      the use of my library.
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   Note: Welcome is used elliptically for you are welcome.
         "Welcome, great monarch, to your own." --Dryden.
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   Welcome-to-our-house (Bot.), a kind of spurge (Euphorbia
      Cyparissias). --Dr. Prior.
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The Collaborative International Dictionary of English v.0.48:

Welcome \Wel"come\, n.
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   1. Salutation to a newcomer. "Welcome ever smiles." --Shak.
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   2. Kind reception of a guest or newcomer; as, we entered the
      house and found a ready welcome.
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            His warmest welcome at an inn.        --Shenstone.
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            Truth finds an entrance and a welcome too. --South.
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   To bid welcome, to receive with professions of kindness.
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            To thee and thy company I bid
            A hearty welcome.                     --Shak.
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WordNet (r) 3.0 (2006):

welcome
    adj 1: giving pleasure or satisfaction or received with pleasure
           or freely granted; "a welcome relief"; "a welcome guest";
           "made the children feel welcome"; "you are welcome to
           join us" [ant: unwelcome]
    n 1: the state of being welcome; "don't outstay your welcome"
    2: a greeting or reception; "the proposal got a warm welcome"
    v 1: accept gladly; "I welcome your proposals"
    2: bid welcome to; greet upon arrival [syn: welcome,
       receive] [ant: say farewell]
    3: receive someone, as into one's house