What's "give slack" mean?

Native speaker’s answer
Rebecca
To "give slack" to someone means to lessen the expectations or to be less harsh on them. Another common phrase you could use is to "cut [someone] slack," which means the same thing as "give slack." Ex: My lecturer gave me some slack. So I'm handing it in on Monday instead of tomorrow. Ex: I hope they cut you some slack for work this week. => to be less harsh