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。