slack·en/`slækən; ˈslækən/ n [I,T] 1 to gradually become slower, weaker, or less active, or to make something do this (使)减慢; (使)变弱,(使)放松: He slackened his speed so I could catch up. 他放慢速度让我跟上。 2 to make something looser, or to become looser (使)松弛,(使)放松: Slacken the screw a little. 把螺丝松一松。