What does "bottleneck" mean?

A point in a process, system, or workflow where the flow slows significantly - reducing the efficiency of the whole operation.

"The approval stage is a bottleneck - everything waits for the director to sign off."
"We need to identify the bottleneck in the supply chain."
"The server is a bottleneck for the whole system."

A bottle's neck is narrower than the body - liquid can only flow as fast as the narrow neck allows, regardless of how much is in the bottle. Apply this to any process.

"The lack of staff is bottlenecking production."

• Process bottlenecks: one slow step slows everything after it
• Resource bottlenecks: one team/machine handles too much
• Approval bottlenecks: decisions require sign-off from a single person

• "Chokepoint" - same concept
• "Constraint" - more formal/lean management: "the constraint in the system"
• "Pinch point" - British alternative
• "Blocking issue" - in project management

Professional and technical. Used in operations, tech, logistics, and project management.