noun
doctor on duty; on-call doctor
Refers to a physician who is currently on duty, especially in a hospital or clinic setting.
当直医師が夜間の急患に対応した。
The doctor on duty handled the nighttime emergency patient.
当直 is a general term for being on duty (night shift, etc.), while 当直医師 specifically refers to a doctor on duty.
Compound of 当直 (on duty) and 医師 (doctor).