Real Dictionary

turn down
phrasal verb: If the rate or level of something turns down, it decreases.
phrasal verb: If you turn down a person or their request or offer, you refuse their request or offer.
phrasal verb: 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.

turn down in American English
to reject (a request, advice, etc.)
to turn over; fold down

turn down in British English
to reduce (the volume or brightness) of (something)
adjective: capable of being or designed to be folded or doubled down
noun: a downturn; a worsening of sales, business, etc