criminal       
 noun [ C ] uk/ˈkrɪm.ɪ.nəl/ us/ˈkrɪm.ə.nəl/
B1 罪犯
someone who commits a crime
  a dangerous/violent criminal 危险的/残暴的罪犯 
 Synonyms: crook (CRIMINAL) culpritevildoerfelon the guilty partymalefactor offenderoutlaw perpetratorvillain wrongdoer 
 - More examples
 - Today's problem child may be tomorrow's criminal.
 - The police officer told the criminal that he had the right to remain silent.
 - If you spend any time in prison, you're labelled as a criminal for the rest of your life.
 - Many of the country's toughest criminals are held in this prison.
 - Many people argue that allowing a criminal to go free is better that imprisoning an innocent person.
 
criminal          
adjective [ before noun ] uk/ˈkrɪm.ɪ.nəl/ us/ˈkrɪm.ə.nəl/
B2 犯罪的;涉及犯罪的
relating to crime
  criminal activity 犯罪活动 
 a criminal act/offence 犯罪行为/刑事犯罪 
 criminal behaviour 犯罪行为 
 a criminal investigation 刑事调查 
  糟糕的;不道德的
very bad or morally wrong
  It's criminal to charge so much for a book. 一本书要这么高的价钱,真是太不应该了。 
 The way we waste this planet's resources is criminal. 我们这样浪费地球的资源简直就是犯罪。 
 - More examples
 - To this day she remains impenitent about her criminal past.
 - When the authorities inquired into his background, they found he had a criminal record.
 - Researchers have just completed the largest-ever survey of criminal behaviour in the UK.
 - She has strenuously denied any criminal wrongdoing.
 - The 19-year-old will be appearing in court on Thursday where she will face criminal charges.