The term 'turn informer' can be defined by three words: RAT, SNITCH, and SQUEAL. A RAT is someone who betrays a friend or colleague by providing information to an authority figure. A SNITCH is someone who gives away confidential information to gain favor or advantage. A SQUEAL is a loud cry of distress or pain, but it can also refer to someone who reveals secrets or incriminating information. All three terms refer to someone who provides information to an authority figure, often at the expense of another person.