im·pe·ri·al·ism 
(ĭm-pîrē-ə-lĭz′əm)
(ĭm-pîrē-ə-lĭz′əm)n.
1. The extension of a nation's authority by territorial acquisition or by the establishment of economic and political dominance over other nations.
2. A political doctrine or system promoting such extension of authority.
im·peri·al·ist adj. & n.
im·pe′ri·al·istic adj.
im·pe′ri·al·isti·cal·ly adv.