"Skill proficiency" refers to having a high level of ability or expertise in a particular skill or area. It means being very skilled or knowledgeable in something. Full definition
Skills proficiency falls off steadily for those in their 30s and older. (canadianbusiness.com)
Requirements Excellent Computer Skills Proficiency in Microsoft... (ziprecruiter.com)
The committee was tasked with determining whether an attorney could ethically list his or her areas of practice in the «Skills and Expertise» section» and if so, could the attorney also use the proficiency categories under the «Skills and Expertise» section, which permit the lawyer to indicate the level of skill proficiency as a beginner, intermediate, advanced or expert. (americanbar.org)