2 Definitions

To separate into elemental parts or basic principles so as to determine the nature of the whole (2) A course of reasoning showing that a certain result is a consequence of assumed premises. (3) (ANSI) The methodical investigation of a problem, and the separation of the problem into smaller related units for further detailed study
defined by 6SixSigSigma
Study and examination of something complex by separating it into more simple component. Typically, includes discovering the parts of the thing being studied, how they fit together, and why they are arranged in a particular way.
defined by PCoE Oregon .Gov