Expertise In A Field

noun a person who is very skilled or experienced in a particular area

adjective denoting a person who has held the position of master in a particular organization or field in the past

• He is a past master in the art of negotiation, always coming out on top.
• My grandpa is a past master at fixing old cars.
• She's a past master at throwing shade during arguments.
• The chef is a past master at creating culinary masterpieces.