Source : Webster's Revised Unabridged Dictionary (1913)

Ambitiousness \Am*bi"tious*ness\ ([a^]m*b[i^]sh"[u^]s*n[e^]s),
   n.
   The quality of being ambitious; ambition; pretentiousness.

Source : WordNet®

ambitiousness
     n : a strong drive for success [syn: {ambition}]