what is the exact meaning of “diplomatic” and how to use that word while speaking?
can anyone clear my confusion?
You know,there are many words including different meanings, but you should remember common meaning. Usually we understand meaning of the word from the context 
definition 1:of or pertaining to diplomacy.The two nations have resumed diplomatic relations.
2)careful not to give offense or appear critical; tactful.
that will be useful wordsmyth.net
The exact meaning(s) and examples of use can be found here:
oxfordadvancedlearnersdictio … diplomatic