n 1  :  a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual  2 a  :  CLEAVAGE 2  b  :  the splitting of an atomic nucleus resulting in the release of large amounts of energy - called also nuclear fission  fis*sion vb fis*sioned  fis*sion*ing   fis*sion*al adj 
 
 also   
 
Similar sounding terms:  fi·cin  vis·na 
 
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