The Collaborative International Dictionary of English v.0.48:

Ambition \Am*bi"tion\, n. [F. ambition, L. ambitio a going
   around, especially of candidates for office is Rome, to
   solicit votes (hence, desire for office or honor), fr. ambire
   to go around. See Ambient, Issue.]
   1. The act of going about to solicit or obtain an office, or
      any other object of desire; canvassing. [Obs.]
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            [I] used no ambition to commend my deeds. --Milton.
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   2. An eager, and sometimes an inordinate, desire for
      preferment, honor, superiority, power, or the attainment
      of something.
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            Cromwell, I charge thee, fling a way ambition:
            By that sin fell the angels.          --Shak.
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            The pitiful ambition of possessing five or six
            thousand more acres.                  --Burke.
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The Collaborative International Dictionary of English v.0.48:

Ambition \Am*bi"tion\, v. t. [Cf. F. ambitionner.]
   To seek after ambitiously or eagerly; to covet. [R.]
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         Pausanias, ambitioning the sovereignty of Greece,
         bargains with Xerxes for his daughter in marriage.
                                                  --Trumbull.
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WordNet (r) 3.0 (2006):

ambition
    n 1: a cherished desire; "his ambition is to own his own
         business" [syn: ambition, aspiration, dream]
    2: a strong drive for success [syn: ambition, ambitiousness]
    v 1: have as one's ambition

The Devil's Dictionary (1881-1906):

AMBITION, n.  An overmastering desire to be vilified by enemies while
living and made ridiculous by friends when dead.