I've have seen the term around and I mostly get that it is referred to when someone reports a vulnerability to Mitre.
But what does this mean practically? Are you listed somewhere as the reporter? Is this something people use on their CVs?
When someone discovers a vulnerability, they can request a Common Vulnerabilities and Exposures (CVE) id. This id will be linked to the vulnerability and is linked to you as a person.
Whether it is used on a resume is totally up to you, I personally started doing this recently in order to show my activities.