a person who concentrates primarily on a particular subject or activity; a person highly skilled in a specific and restricted field:he is a specialist in psychometric testing [with modifier]:the study was undertaken by a market-research specialist
a person highly trained in a particular branch of medicine:her doctor thought her allergy was psychosomatic, but he sent her to a specialist
adjective
possessing or involving detailed knowledge or study of a restricted topic:you may require specialist financial advice
[attributive] concentrating on a restricted field, market, or area of activity:a specialist electrical shop