-imperialize-

n. 1. The power or character of an emperor; imperial authority; the spirit of empire. [ 1913 Webster ]

Roman imperialism had divided the world. C. H. Pearson. [ 1913 Webster ]

2. The policy, practice, or advocacy of seeking, or acquiescing in, the extension of the control, dominion, or empire of a nation, as by the acquirement of new, esp. distant, territory or dependencies, or by the closer union of parts more or less independent of each other for operations of war, copyright, internal commerce, etc. The practise of building or extending an empire. [ Webster 1913 Suppl. +PJC ]

The tide of English opinion began to turn about 1870, and since then it has run with increasing force in the direction of what is called imperialism. James Bryce. [ Webster 1913 Suppl. ]