A methodology is a set of principles, rules, and processes that guide the business analysis activities and deliverables within a project or organization. A methodology can be based on a standard, such as the BABOK Guide, or a specific framework, such as Waterfall or Agile. A methodology helps the business analyst to plan, execute, monitor, and control the business analysis work in a consistent and effective way. References:

BABOK Guide, Chapter 2: Business Analysis Planning and Monitoring, Section 2.1: Plan Business Analysis Approach, p. 24-25

Business Analysis Methodology | What is this and is it real?