As nouns the difference between imperialism and colonialist
is that imperialism is the policy of forcefully extending a nation's authority by territorial gain or by the establishment of economic and political dominance over other nations while colonialist is an advocate of colonialism.
As an adjective colonialist is
of or pertaining to colonialism.
imperialism
Noun
(-)
The policy of forcefully extending a nation's authority by territorial gain or by the establishment of economic and political dominance over other nations.
See also
* imperialist
* imperialistic