Enterprise architecture (EA) is "a well-defined practice for conducting enterprise analysis, design, planning, and implementation, using a holistic approach at all times, for the successful development and execution of strategy. Enterprise architecture applies Architecture principles and practices to guide organizations through the business, information, process, and technology changes necessary to execute their strategies. These practices utilize the various aspects of an enterprise to identify, motivate, and achieve these changes."

Source: The Federation of Enterprise Architecture Professional Organizations (FEAPO): A common perspective on enterprise architecture (published in Architecture & Governance magazine).

In Wikipedia (where above definition can be found as well): Enterprise Architecture

As explained in Enterprise models for the #2030Agenda we advocate the use of a combination of the ArchiMate Framework and the Federal Enterprise Architecture Framework for the elaboration of enterprise architecture models. We use Archi - The Free ArchiMate Modelling Tool for creating and sharing the models that we make for the Addis Ababa Action Agenda.