Japanese Kanji "大望(たいぼう-taibou)" means ambition. And also another word "大志(たいし-taishi)" has almost same meaning.
Often some Japanese words such as "野望(やぼう-yabou)" or "野心(やしん-yashin)" are used for the meaning of ambition but these two words have some negative or bad meaning aspect. So most of the Japanese have not so good feeling against of these two words(野望 and 野心).
So for purely great ambition, we use 大望 and 大志 in Japan.