Definition of Deviation Request
A deviation request asks for permission to make a product (or service) that does not comply with certain requirements, within certain limits.
This is pre-realisation.
In contrast, a non-conformance report (NCR) is a post-realisation documentation of a nonconformity - meaning that the intention was to conform to requirements but something went wrong.
With either of these cases, a review process needs to decide what to do.
Approval of a deviation request comes in the form of a deviation permit, although other terms are sometimes used.