See: TURN IN(1).
To give to someone; deliver to someone. * /I want you to turn in a good history paper./ * /When the football season was over, we turned in our uniforms./ 2. To inform on; report. * /She turned them in to the police for breaking the street light./ 3. To give in return for something. * /They turned in their old money for new./ * /We turned our car in on a new model./ Syn.: TRADE IN. 4. {informal} To go to bed. * /We were tired, so we turned in about nine o'clock./ Contrast: TURN OUT(4).