Blockers

Blockers are any factors, objects, or agents that prevent progress toward a goal. The term is used across disciplines to describe impediments or devices that halt activity, whether in planning, execution, or biological systems. In everyday use, blockers can be practical obstacles, policy constraints, or chemical or biological agents that inhibit a process.

In project management and software development, a blocker is an issue that stops work on a task or feature until it is resolved. Common blockers include missing information, unavailable resources, technical defects, or external dependencies. Teams track blockers in issue trackers, assign ownership, and set targets for resolution to restore momentum.

In biology and medicine, blockers are agents that inhibit a biological process. A receptor blocker, or antagonist, prevents a ligand from activating a receptor. Pharmacological blockers such as beta blockers or calcium channel blockers are used to modulate cardiovascular function and other systems. The term can also refer to substances that obstruct signaling pathways or enzymatic activity.

In sports, blockers are players whose role is to impede opponents or protect teammates. In American football, offensive linemen and other players act as blockers to create space for ball carriers. In hockey and some other sports, defensemen or forwards may be described as blockers when they prevent shots or passes.

In computing, blocking describes operations that halt program progress until a condition is met or a resource becomes available, such as blocking I/O or synchronization primitives. Non-blocking alternatives allow the program to continue work while waiting.