IPA: /nɒnˈdɪpləˌmætɪk/
KK: /nɑnˈdɪpləˌmætɪk/
Not relating to diplomacy or diplomatic relations; often used to describe actions or statements that are blunt or not tactful.
His nondiplomatic remarks during the meeting surprised everyone.
Nondiplomatic → It is formed from "non-" (meaning not) and "diplomatic" (from Greek "diplomatikos", meaning relating to a diploma or official document). The word "nondiplomatic" means not relating to diplomacy or official negotiations.
Think of 'non-' meaning not, and 'diplomatic' relating to official matters — so nondiplomatic describes something that is not related to official negotiations.