This is a vague term which should never be used, unless the applicant is an athlete or entertainer. For instance, I have had many successful clients in this category who are scientists in their early 30s. The rumor about a specific number of publications is even more alarming because it is entirely untrue. The regulations do not even require publications. Please recall that only 3 of 10 indicators need be met.
Publications are only one indicator.
In addition, the INS has never set any minimum number of publications and I have had many successful applicants with far less than 50 publications. The INS is more interested in the quality and significance of publications. One article in a major international peer-reviewed journal is worth several articles in minor journals. The simple fact is that the federal regulations are no longer an adequate indicator of the requirements of this category because the INS has promulgated so many interpretations of individual sentences within the regulations. The only way to obtain an accurate assessment of the chances of success in this category is to seek the counsel of an experienced attorney.