1.
If you turn down a person or their request or offer, you refuse their request or offer.
Before this I’d have smiled and turned her down...
Would you turn down $7,000,000 to appear nude in a magazine?
= reject
PHRASAL VERB : V n P , V P n (not pron)
2.
When you turn down a radio, heater, or other piece of equipment, you reduce the amount of sound or heat being produced, by adjusting the controls.
He kept turning the central heating down...
She could not bear the relentless music and turned down the volume.
≠ turn up
PHRASAL VERB : V n P , V P n (not pron)