freak

Noun

• someone who is so ardently devoted to something that it resembles an addiction
  • a golf addict
    
  • a car nut
    
  • a bodybuilding freak
    
  • a news junkie
    

• a person or animal that is markedly unusual or deformed

Verb

• lose one's nerve
  • When he saw the accident, he freaked out
    

Related words

• Synonyms: 
  addict , nut , junkie , junky , monster , monstrosity , lusus naturae , freak out , gross out