The act of consolidating power under a central control WordNet 3.0 & Open English WordNet

Centralisation or centralization is the process by which the activities of an entity or organization, particularly those regarding planning, decision-making and control of strategies and policies, become concentrated within a particular group, sector, department or region within that entity or organization. Wikipedia

Process by which the activities of an organisation become concentrated within a particular location and/or group Wikidata

The concentration of decision-making responsibility in the hands of managers at the top of an organisation. OmegaWiki

The act or process of centralizing, or the state of being centralized; the act or process of combining or reducing several parts into a whole. Wiktionary

The act or process of centralizing. Wiktionary (translation)