down-turn folder向下折边器
down-turn hemming device向下卷边器
step-down turn ratio降压匝比
N-COUNT（可数名词） If there is a downturn in the economy or in a company or industry, it becomes worse or less successful than it had been. 衰退
They predicted a severe economic downturn.
他们预言将会有一次严重的经济衰退。