The word "slack" has a few different meanings. In the first set of examples, a person who slacks (off), takes it easy or does a minimal amount of work.
David is slacking off at work.
He’s kind of a slacker. (slacker = a person who avoids work)
Employees who slack off at work may eventually get fired.
Don’t be a slacker.
Look at these slackers slacking off, again!
The word "slack" is also used as a noun when reducing the amount of tension in tightly pulled wire, string, or rope.
Give me some slack.
I need more slack.
There’s too much slack on this rope.
The chain on this chainsaw needs a little more slack; otherwise, the chainsaw is going to burn out.
As a noun, "slack" also refers to an amount of personal space or tolerance of particular human behavior.
I can’t be perfect. You’ve got to give me some slack.
Can’t you give me a little more slack?
The teacher decided to be less strict and gave the students more slack.
If you give him too much slack, he’s going to misbehave.
The managers at the company gave their employees a little more slack to get their work completed after a deadline had passed.
The word "slacks" is a plural noun that refers to a pair of pants.
She wears slacks to work.
The uniform consists of black slacks and a white shirt.
These slacks need to be ironed.
You have to keep slacks on a hanger in order to maintain the crease in the pants. (crease = the raised center of the pants which creates a neat appearance)
The slacks match her jacket.
Note: Slack is also a technology company that make collaboration within and among companies easier.