What does slack mean?
Slack has several connected but distinct meanings. As an adjective, it most commonly means not tight or firmly fastened, as in a slack rope. It can also describe careless or insufficiently rigorous conduct, such as slack standards or slack safety procedures. In organizations, engineering, and project management, slack refers to unused capacity, extra time, or inefficiency within a system: cutting the slack means removing waste or delay. As a noun, slack can refer to a period of reduced activity, such as the slow season in a business. The word can also mean negligence or lack of effort, making it often mildly critical in formal contexts. Although it may simply describe something loose, in social and workplace language it often implies insufficient attention, control, or efficiency. The plural slacks has a separate traditional use for casual trousers.
Not tight or firmly fastened; lacking tension or firmness.
"He tightened the slack belt around the equipment."
The adjective is often used for rope, cables, belts, and other objects that are not under sufficient tension.
Lacking in care, effort, attention, or rigor.
"The company was criticized for its slack approach to customer complaints."
This use is commonly critical and is often applied to standards, discipline, procedures, or performance.
Characterized by insufficient capacity, speed, coordination, or efficiency.
"The engineers identified slack in the production schedule."
In technical and organizational contexts, slack refers to spare capacity or unused time that can often be reduced.
A lack of tension, care, effort, or attention; also a period of reduced activity.
"There was too much slack in the workflow, so the team simplified the approval process."
The sense of wasted capacity is especially common in business, engineering, and project-management usage.
The plural form is used for casual or informal trousers, particularly in American English.
"He wore a pair of slacks to the informal office event."
Slack can describe a loose rope, relaxed standards, or wasted capacity—the common thread is something not being held as firmly or effectively as it should be.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of slack
The adjective and noun meanings of slack descend from Old English slæc, which was related to senses involving looseness, remissness, and lack of tension. The word developed through Middle English, where it could describe physical looseness as well as negligence or insufficient effort. The modern organizational sense, referring to unused capacity or inefficiency, is a later metaphorical extension of the older ideas of looseness and lack of tension.
Related word forms
How slack is actually used
In business and technical contexts, slack often refers to spare capacity, unused time, or inefficiency. As a noun, it can mean a period of reduced activity, and the plural form slacks is chiefly used for informal or casual trousers, especially in American English.
Easily confused with slack
Both can describe insufficient strictness or attention, but lax more often characterizes rules, discipline, or enforcement, whereas slack more often describes looseness, reduced effort, or inefficiency.
Slack is an adjective or noun, while slacken is a verb meaning to become less tight, active, or forceful.