405 Method Not Allowed - Client Error Response Status Code

Official Definition

The 405 (Method Not Allowed) status code indicates that the method received in the request-line is known by the origin server but not supported by the target resource. The origin server MUST generate an Allow header field in a 405 response containing a list of the target resource's currently supported methods.

A 405 response is cacheable by default; i.e., unless otherwise indicated by the method definition or explicit cache controls.