Final answer:
Imperialism refers to the economic, political, and military domination of a stronger nation over weaker nations for the purpose of gaining resources and markets.
Step-by-step explanation:
Imperialism, in the context of modern history, refers to the economic, political, and military domination of a stronger nation over weaker nations. It involved the conquest and control of foreign territories for the purpose of gaining access to natural resources and markets. This expansion of European empires in the nineteenth century led to the control of over 80% of the world's surface by European powers before World War I.