killer vs serial killer

killer

noun
  • One who or that which kills. 

  • A particularly heavy type of handstamp, or portion of one, often obscuring a large part of the postage stamp. 

  • A knockout form of darts or pool involving several players. 

  • That which causes stress or is extremely difficult, especially that which may cause failure at a task. 

  • Synonym of virama (“kind of diacritical mark”) 

  • A remarkably impressive person or thing. 

  • Something that is so far ahead of its competition that it effectively kills off that competition. 

  • A club used for killing fish. 

adj
  • Causing death, destruction, or obliteration. 

  • Excellent, very good, cool. 

  • Distressing, uncomfortable. 

serial killer

noun
  • A person who commits multiple (more than two) murders, especially similar ones with no obvious motive over a period of time with a "cooling-off" period between each murder. 

How often have the words killer and serial killer occurred in a corpus of books? (source: Google Ngram Viewer )