define birth defect
birth defect. n. A physiological or structural abnormality that develops at or before birth and is present at the time of birth, especially as a result of faulty development, infection, heredity, or injury. Also called congenital anomaly.. Any distortion of a part or general disfigurement of the body. 2. Congenital malformation, see there. 3. An abnormality of structure, function or body metabolism present at birth that may result in a physical and/or mental disability or is fatal. (bÄ­rth dÄfekt).