A Minor Nation or "MN" in Imperialism and Imperialism 2 is a nation that cannot be played by human players, who can play only as Great Powers but can explore and set up trade consulates and embassies in, and trade with, MNs and offer subsidies and grants with a view to acquiring influence and eventually full or partial control by either diplomacy or conquest.
Each MN has a capital province and a few other provinces. The Capital is a port and links to a sea in the same way as GP capitals and ports do.
There are ten minor nations in the New World. They are often called "tribes". Rules for them are slightly different; for example, you can invade one without a formal declaration of war, and they do not start with forts.