Imperialism has two meanings, one describing an action and the other describing an attitude. Most commonly it is understood in relation to Empire building, as the expansion of a nation's authority by territorial conquest establishing economic and political powers in other territories or nations, and when such encompasses non-contiguous "colonies" or "protectorates" then the term also subsumes Colonialism. In that sense, most European seafaring powers were at one time or another Colonialistic and therefore Imperialistic, regardless of their exploitation or benevolence toward their colonial possessions and people.
In its second meaning the term describes the imperialistic attitude of superiority, subordination and dominion over foreign people— a chauvinism and comportment relegating foreign people to a lesser social and or political status. To clarify the distinction, the French colonies in North America treated the native races with great diplomacy, whereas the British colonies early on began treating native Americans chauvinistically, as savages and lesser creatures.
Imperialism is often autocratic, e.g. in early 20th century Japan, and sometimes monolithic in character. While the term imperialism often refers to a contiguous political or geographical domain such as the Ottoman Empire the Russian Empire, or the British Empire, etc the term can equally be applied to domains of knowledge, beliefs, values and expertise, such as the empires of Christianity (see Christendom) or Islam (see Caliphate).
Currently, there is an effort to broaden the definition of "imperialism" so it applies to any instance of a greater power acting or being perceived to act at the expense of a lesser power. Including 'perception' in the definition makes it circular, solipsistic, and subjective. Under this broader definition, 'imperialism' not only describes colonial, territorial policies;but also describes economic dominance and influence.
European dominance of the east through economic exploitation and political rule, (as distinct from the word colonialism, which usually implied establishment of settler colonies often with slavery as the labor system), the word was coined in the mid-nineteenth century.