Definition from Wiktionary, the free dictionary
See also turn-up
- (intransitive) To show up; to appear suddenly or unexpectedly.
- Is this your pencil that turned up in my drawer?
- I don't like people turning up without an appointment.
- (transitive) To increase the amount of something by means of a control, such as the volume, heat, or light.
- Turn up the radio and sing along.
- (transitive) To reposition by rotating, flipping, etc. upwards.
- He turned up his collar against the cold.
- (transitive, nautical) To belay or make fast a line on a cleat or pin.
Usage notes 
- In senses 2, 3 and 4 the object is normally a thing, not a person. It may appear before or after the particle. If the object is a pronoun, then it must be before the particle.
- (increase): turn down
Derived terms 
to appear unexpectedly
increase volume etc.
- A stroke of good luck.