Slackest

adjective

1. (normally said of a rope) Lax; not tense; not firmly extended.

   "a slack rope"

2. Weak; not holding fast.

   "a slack hand"

3. Lacking diligence or care; not earnest or eager.

   "slack in duty or service"

4. Not active,successful, or violent.

   "Business is slack."

5. Excess; surplus to requirements.

   "the slack capacity of an oil pipeline"