Explains a lot when your understanding of the subject is based on a superficial duck duck go search. Imperialism represents a predatory, exploitative system where advanced capitalist nations dominate and exploit weaker nations for resources, markets, and profit. A country going to war is not itself a sign of imperialism, and anybody who actually bothered to understand the causes for the war in Ukraine would know that it was the west that was establishing economic and political dominance over Ukraine.

Yes, Marxists use the latter definition listed, not the bolded, because it's a process that is trackable and explainable within itself. Adding "invasion" to the mix only makes sense if it is as a consequence of the latter, otherwise you can just call it invasion.