Source : Webster's Revised Unabridged Dictionary (1913)

Zeeman effect \Zee"man ef*fect"\ (Physics)
   The widening and duplication, triplication, etc., of spectral
   lines when the radiations emanate in a strong magnetic field,
   first observed in 1896 by P. Zeeman, a Dutch physicist, and
   regarded as an important confirmation of the electromagnetic
   theory of light.