slack³ (also slack off) verb [intransitive]
to make less effort than usual, or to be lazy in your work:
He was accused of slacking and taking too many holidays.

[TahlilGaran] Dictionary of Contemporary English ▲

slack off
1.
to work less hard than is usual or necessary.
Workers tend to slack off on Mondays and Fridays.

2.
to become less severe or extreme.
If this rain would slack off, we could finish the work outside.

[TahlilGaran] English Idioms Dictionary ▲

slack off
to reduce something gradually, to become less active, to become lazy
Recently I have begun to slack off in my effort to find a new job.

[TahlilGaran] English Idioms Dictionary ▲

slack off
v. phr.
1. To become less active; grow lazy.
Since construction work has been slacking off toward the end of the summer, many workers were dismissed.
2. To gradually reduce; taper off.
The snowstorms tend to slack off over the Great Lakes by the first of April.

[TahlilGaran] English Idioms Dictionary ▲