noun
- Hal·dan Kef·fer [hawl-duh n kef-er] /ˈhɔl dən ˈkɛf ər/, 1903–83, U.S. physiologist: Nobel Prize in Medicine 1967.
- American biophysicist. He shared a 1967 Nobel Prize for research on the physiological and electrical activities of the optic nerve and the eye.