adjective.of or relating to the internal affairs of a major political unit (such as a nation)

• … municipal legislation … enacted for the fulfillment of the treaties …
• municipal government

adjective.of, relating to, or characteristic of a municipality

• municipal water supplies
• municipal elections

adjective.having local self-government

• municipal courts
• a municipal building

noun.a security issued by a state or local government or by an authority set up by such a government —usually used in plural