cut sb some slack的定义：to not judge someone as severely as you usually would because they are having problems at the present time.也就时说,当某人表现不好或者犯错的时候,如果情有可原,就可以cut him/her some slack,类似中文里的“放某人一马”.举几个例子：
Tom is often late for work these days,but I’m sure boss will cut him some slack.After all,his wife just died.（Tom最近老迟到,不过我相信头儿一定不会追究.毕竟,他的妻子刚去世.）
I know you’ve been through a lot,so I’m willing to cut you some slack here.But,don’t you yell at me again,okay?Enough is enough.（我知道你最近不好受,所以我愿意放你一马.但是,以后别再对着我大吼大叫了!适可而止,别太过分.）