the world > relative properties > quantity > decrease or reduction in quantity, amount, or degree > decrease in quantity, amount, or degree [verb (intransitive)] > become toned down (2)
intransitive for passive. to tone down, to become lowered, weakened, or softened in tone; to tone up, to rise or improve in tone.
To become sober, in various senses. Also with off and up. Hence as attributive.phr.