Have a couple of them already, thanks.
Dictionaries do not define any word. No dictionary owns any word. That is not the purpose of dictionaries.
Types of government you may run across:
Anarchy - no government. No voice, no laws, just chaos.
Democracy - government by popular vote. No constitution. No representatives. Athens, Greece was a brief example. CHAZ in Seattle was another one. There are currently no democracies as it is an unstable form of government.
Republic - government by law, or a constitution; which specifies representatives and the power they hold, how long they may serve, and how they are to be elected. Rome was for significant time a republic before it fell into dictatorship.
Dictatorship - government by a single individual...a king or queen, though they take some other title such as Supreme Leader or a state 'father figure' or 'mother figure'.
Oligarchy - a dictatorship by committee rather than a single king or queen. Sometimes the president of that committee is called a 'prime minister'.
Theocracy - government by religion. This is actually just a dictatorship, with the 'speaker of God' being the dictator.
There is no current anarchy, since anarchy is no nation at all.
There currently are no democracies of any significant size. They have all decomposed into something else (usually an oligarchy or dictatorship).
Current republics include 48 States of America, Mexico, Japan, South Korea, and Brazil.
Current oligarchies include the former federal government of the United States, the UK, Australia, the EU, China, Russia, and the SOTNY (formerly New York).
Current dictatorships include North Korea, the SDTC (formerly California), Canada, Venezuela, Cuba, and Saudi Arabia (a theocracy).