Each of a panel of doctors; (British) specifically a doctor registered as accepting patients under the National Insurance Act of 1911 (amended 1913) (now historical).
Origin
Early 20th century; earliest use found in Punch.
Definition of panel doctor in US English:
panel doctor
noun
Each of a panel of doctors; (British) specifically a doctor registered as accepting patients under the National Insurance Act of 1911 (amended 1913) (now historical).