1. past tense of slack; became loose or less tight
2. past tense of slack; reduced effort or intensity; became lazy or negligent

Examples

• The rope slacked when the weight was removed.
• His grip slacked as he grew tired.
• She slacked off during the final weeks of school.
• The team slacked in their training over the summer.
• The cable slacked and needed to be retightened.
• He slacked his pace as he approached the finish line.
• The students slacked on their homework assignments.