The Collaborative International Dictionary of English v.0.48:

Magnanimous \Mag*nan"i*mous\, a.[L. magnanimus; magnus great +
   animus mind. See Magnate, and Animus.]
   1. Great of mind; elevated in soul or in sentiment; raised
      above what is low, mean, or ungenerous; of lofty and
      courageous spirit; as, a magnanimous character; a
      magnanimous conqueror.
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            Be magnanimous in the enterprise.     --Shak.
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            To give a kingdom hath been thought
            Greater and nobler done, and to lay down
            Far more magnanimous than to assume.  --Milton.
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   2. Dictated by or exhibiting nobleness of soul; honorable;
      noble; not selfish.
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            Both strived for death; magnanimous debate.
                                                  --Stirling.
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            There is an indissoluble union between a magnanimous
            policy and the solid rewards of public prosperity
            and felicity.                         --Washington.
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WordNet (r) 3.0 (2006):

magnanimous
    adj 1: noble and generous in spirit; "a greathearted general";
           "a magnanimous conqueror" [syn: greathearted,
           magnanimous]
    2: generous and understanding and tolerant; "a heart big enough
       to hold no grudges"; "that's very big of you to be so
       forgiving"; "a large and generous spirit"; "a large heart";
       "magnanimous toward his enemies" [syn: big, large,
       magnanimous]