noun

1. the highest-ranking diplomatic representative appointed by one country or government to represent it in another
2. a special representative: an ambassador-at-large is one accredited to no particular country; an ambassador extraordinary is one on a special diplomatic mission; an ambassador plenipotentiary is one having the power to make treaties
3. an official agent with a special mission
4. an unofficial representative or messenger an ambassador of goodwill

Etymology: ME ambassatour < MFr ambassateur < OIt ambasciatore < Prov ambaissador < *ambaissa, mission, task < Goth andbahti, office, service < Celt *amb(i)actos, a messenger, servant (> L ambactus, a vassal) < IE *ambhi-, about (see ambi-) + base *aĝ-, to do (see act)