slacken off
词形变化：
动词过去式: slackened | 动词过去分词: slackened | 动词现在分词: slackening | 动词第三人称单数: slackens |
同义词：
loosen | relax | release | slacken off | unbend | soften | silence | alleviate | lessen | lower | delay | slack | remit | slow down | slow up | slack up | slow |
反义词：
quicken |