For sure, but there are a few problems with that definition. The first is that it doesn't apply to the Russian intervention in Ukraine that started this conversation, which is neither unprovoked nor being done to expand Russian territory.
The second is that it only includes atate actions meant to take territory in an official capacity, while many imperialist actions have been carried out under the auspices of private companies like Haliburton, Dole, the United Fruit Company, and the Dutch East India Company.
The third is that we already have the term Expansionist, which is perfectly fine and general enough for both capitalist and non-capitalist actions, while Imperialism describes a specific dynamic that arises from specifically capitalist causes.
That's great, but now that you're here go ahead and answer the question. When a colonized country throws off it's chains, whose fault is it when the colonizer retaliates?