The Collaborative International Dictionary of English v.0.48:

Magnanimity \Mag`na*nim"i*ty\, n. [F. magnanimit['e], L.
   magnanimitas.]
   The quality of being magnanimous; greatness of mind;
   elevation or dignity of soul; that quality or combination of
   qualities, in character, which enables one to encounter
   danger and trouble with tranquility and firmness, to disdain
   injustice, meanness and revenge, and to act and sacrifice for
   noble objects.
   [1913 Webster]

WordNet (r) 3.0 (2006):

magnanimity
    n 1: liberality in bestowing gifts; extremely liberal and
         generous of spirit [syn: munificence, largess,
         largesse, magnanimity, openhandedness]

Moby Thesaurus II by Grady Ward, 1.0:

89 Moby Thesaurus words for "magnanimity":
   ambition, ambitiousness, benevolence, bigheartedness, bigness,
   bounteousness, bountifulness, bounty, careerism, charitableness,
   charity, chivalrousness, chivalry, climbing, condonation,
   consequence, disregard, distinction, easiness, easy purse strings,
   elevation, eminence, errantry, exaltation, fame, forbearance,
   forgiveness, forgivingness, free hand, freedom, freehandedness,
   freeheartedness, freeness, generosity, generousness, givingness,
   glory, graciousness, great heart, greatheartedness, greatness,
   greatness of heart, heroism, high-mindedness, hospitality,
   idealism, indulgence, kindness, knight-errantry, knightliness,
   largeheartedness, largeness, largess, lenience, leniency, lenity,
   liberality, liberalness, loftiness, lofty ambition, long-suffering,
   longanimity, magnanimousness, majesty, munificence, nobility,
   noble-mindedness, nobleness, notability, open hand, open heart,
   openhandedness, openheartedness, overlooking, patience,
   permissiveness, power-hunger, princeliness, prominence, renown,
   social climbing, status-seeking, sublimity, tolerance, toleration,
   unrevengefulness, unselfishness, vaulting ambition, welcome