1.
If you say that someone or something turns up, you mean that they arrive, often unexpectedly or after you have been waiting a long time.
Richard had turned up on Christmas Eve with Tony...
= show up
PHRASAL VERB: V P
2.
If you turn something up or if it turns up, you find, discover, or notice it.
Investigations have never turned up any evidence.
...a very rare 15th-Century spoon, which turned up in an old house in Devon.
PHRASAL VERB: V P n (not pron), V P
3.
When you ~ a radio, heater, or other piece of equipment, you increase the amount of sound, heat, or power being produced, by adjusting the controls.
Bill would ~ the TV in the other room...
I turned the volume up...
Turn the heat up high.
? turn down
PHRASAL VERB: V P n (not pron), V n P, V n P adj