"Extensive expertise" refers to having a vast amount of knowledge, skills, and experience in a specific field or subject. It means that someone is highly knowledgeable and skilled in a particular area. Full definition
A skilled, driven, pragmatic IT support professional with extensive expertise in installation and software repairs. (resumemycareer.com)
A skilled, driven, pragmatic maintenance professional with extensive expertise in managing and providing automotive parts and service. (resumemycareer.com)
Together we have extensive expertise of running and winning personal injury compensation claims on behalf of injured members. (thompsonstradeunion.law)