Pronunciation: (am-bas'u-dur, -dôr"),[key] —n. 1. a diplomatic official of the highest rank, sent by one sovereign or state to another as its resident representative (ambas'sador extraor'dinary and plenipoten'tiary). 2. a diplomatic official of the highest rank sent by a government to represent it on a temporary mission, as for negotiating a treaty.
3. a diplomatic official serving as permanent head of a country's mission to the United Nations or some other international organization.
4. an authorized messenger or representative. Abbr.: Amb., amb.