to tell someone in authority about something wrong that someone you know has done - used especially by children:
Please don't tell on me - my parents will kill me if they find out!
WORD CHOICE: WORD CHOICE: say, tell, give, askYou use saywhen you are mentioning someone's exact words• 'Hello,' she said. • Someone said, 'Let's go!'Saycan be followed by 'that'• He said that he was tired. In speech people often leave out 'that'• They said there had been a mistake.Saycan be followed by 'something', 'anything', 'nothing', or 'so'• Did you say something? • Nobody dared to say anything. • You have to come - Dad said so.It can also be followed by 'goodbye' or 'hello'• I'll just go and say hello to David.Apart from these uses, sayis not normally followed by an object. For example, it cannot be followed by 'a story', 'a lie', 'some information', or 'an answer'. You tella story, a joke, a lie, or the truth• They told a funny story about their trip. You giveinformation, an order, an instruction, or an answer• He gave no reply.!! You do not say a question. You aska question• Can I ask a question?You can say something tosomeone• Has he said something to you?When talking about giving information, it is more usual to say that you tell someone something• Clare told us something interesting (NOT said us something...). • Can anyone tell me what time it is? (NOT say to me what...) You can tell someone about something• Did you tell Lucy about the party? (NOT say to Lucy about...)You cansay to dosomething, but it is more usual totell someone to dosomething• The teacher told us to open our books (NOT said us/said to us to...). ➔ See alsosay
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.