Territorialize, which means to mark or claim a territory, has several synonyms in the English language. One of the most common synonyms is "demarcate," which refers to marking or determining the boundaries of a particular area. Another term that is often used in place of territorialize is "colonize," which implies the establishment of a colony or settlement within a previously unsettled area. "Occupying" and "annexing" are also substitutes for territorialize, as they imply taking control over a certain territory or land. Overall, there are many ways to describe the act of claiming or marking a territory, and these synonyms can help convey a differentiated meaning or connotation depending on the context in which they are used.