What is a back-out plan in project management?

Question

In Project Management we talk about:

1) Contingency Plan
2) Back-up Plan
3) Fall-back Plan
4) Back-out Plan

How do they differ from one another?

Answer 1

A project back out plan is a term used in usually in IT (especially software development) projects.

A project back out consists of restoring the system to its previous state (prior to rolling out the product) if the product proved to be buggy or causing issues with the users.

I personally think that a project back out plan falls under product management and not project management - but it seems that many project managers take care of this (instead of product managers).