IPA: /æmˌbæsəˈdɔːrɪəl/
KK: /æmˌbæsəˈdɔrɪəl/
Relating to a person who represents their country in a foreign place, especially in diplomatic matters.
The ambassadorial duties require a great deal of diplomacy and tact.
Ambassadorial is formed from "ambassador" (from Latin "ambassador", meaning one sent on a mission) and the suffix "-ial" (meaning relating to or characterized by). The word "ambassadorial" refers to something that is related to or characteristic of an ambassador or their duties.
Think of an ambassador as someone 'sent on a mission' ('ambassador') and remember that 'ambassadorial' describes things related to that role.