operating surgeon; surgeon performing an operation
Refers specifically to the surgeon who actually performs the surgery, as opposed to an assistant or a surgeon in general. Often used in medical contexts or news reports.
See also: 外科医
The operating surgeon explained the procedure to the patient before the surgery.
彼はその病院で心臓外科の執刀医を務めている。
He serves as the operating surgeon for cardiac surgery at that hospital.
Compound of 執刀 (しっとう, 'holding a scalpel; performing surgery') + 医 (い, 'doctor').