Here is my take on trying to define Enterprise Architecture:
It is a methodology
that provides a process, guidelines and techniques that help in developing an 'Enterprise Landscape' consisting of its Business Processes, its IT applications, its Data and its supporting Infrastructure (including their geographical spread)
thus enabling the enterprise to optimize and manage complexity, respond quickly to changes and align itself to the enterprise's Strategic Goal and Objectives
with clear transitional steps from the current state to the desired state, in the least disruptive way possible.