n 1  :  a natural cleft between body parts or in the substance of an organ: as  a  :  any of several clefts separating the lobes of the liver  b  :  any of various clefts between bones or parts of bones in the skull  c  :  any of the deep clefts of the brain : esp  :  one of those located at points of elevation in the walls of the ventricles - compare SULCUS   d  :  ANTERIOR MEDIAN FISSURE : also  :  POSTERIOR MEDIAN SEPTUM  2  :  a break or slit in tissue usu. at the junction of skin and mucous membrane < of the lip>   3  :  a linear developmental imperfection in the enamel of a tooth fis*sured adj 
 
 Brit also   
 
Similar sounding terms:  fis·su·ra  Fos·sar·ia  viscera 
 
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