We Marxist-Leninist-Maoists follow Lenin in our conception of what imperialism is in the modern capitalist era. That is to say, we use the term imperialism (or what we often also refer to as capitalist-imperialism, to be clearer) in a sense somewhat different from the traditional sense of imperialism in the ancient world, or even in the earlier capitalist period.
Imperialism, in this Leninist sense, is the modern stage of capitalism:
“Imperialism is capitalism in that stage of development in which the dominance of monopolies and finance capital has established itself; in which the export of capital has acquired pronounced importance; in which the division of the world among the international trusts has begun; in which the division of all territories of the globe among the biggest capitalist powers has been completed.” —Lenin
Note that there have been some secondary changes in the situation since Lenin’s time. For example, “international trusts” now generally take the form of Multinational (or Transnational) Corporations (MNCs or TNCs). Similarly, the former direct colonies owned as exclusive preserves by individual capitalist powers are now most often nominally independent neocolonies open to more general predation by all the capitalist power centers. But in its essence Lenin’s definition of capitalist-imperialism is still completely valid, and the one we still adhere to.
Lenin also stated that “If it were necessary to give the briefest possible definition of imperialism we should have to say that imperialism is the monopoly stage of capitalism.”
Imperialism in the ancient or traditional sense, of being simply the domination and economic exploitation of one country by another, is still an essential aspect of imperialism in the Leninist sense. Imperialism, in the narrow sense of a country being dominated and exploited by one or more other countries, in fact characterizes modern capitalism as much as monopoly does, and is essential to it. But now there is a lot more to what we mean by imperialism. As explained by one recent writer:
“We Marxist-Leninists seek not merely to describe the political surface of society, but to probe the material underpinnings and bring to light the economic factors and relationships which lead to those political circumstances. Lenin made the choice to use the term ‘imperialism’ not just to refer to certain political policies of aggression, conquest, and foreign control, but more importantly to refer to an economic system that depends upon such ‘policies’ for its very existence. This is a profound new meaning for the term ‘imperialism’.”
 V. I. Lenin, “Imperialism, the Highest Stage of Capitalism: A Popular Outline”, (Peking: FLP, 1975 (1916)), p. 106. Online in a slightly different translation from Lenin’s Selected Works, vol. 1, (Moscow: 1963), at: http://www.marxists.org/archive/lenin/works/1916/imp-hsc/
 Ibid., p. 105.
 Scott H., “Lenin on Imperialism” (circa 2007), online at http://www.massline.org/PolitEcon/ScottH/LeninOnImperialism.pdf