Longman Dictionary of Contemporary English - investigate

~ v 1 to try to find out the truth about something such as a crime, accident, or scientific problem  (The allegations were investigated, and found to be untrue. | I heard a noise and went downstairs to investigate.) 2 to try to find out more about someone's character, actions etc, because you think they may have been involved in a crime  (Penney was already being investigated by the police on suspicion of murder.) investigation ~ n 1 an official attempt to find out the reasons for something such as a crime, accident, or scientific problem  (a criminal investigation) + into  (The authorities are planning to launch a full-scale investigation into the crash which claimed over 200 lives.) 2 the act of investigating something  (the investigation of computer fraud | under investigation (=being investigated))  (The whole issue is still under investigation.)