Source : WordNet®

bottleneck
     n : a narrowing that reduces the flow through a channel [syn: {constriction},
          {chokepoint}]
     v 1: slow down or impede by creating an obstruction; "His
          laziness has bottlenecked our efforts to reform the
          system"
     2: become narrow, like a bottleneck; "Right by the bridge, the
        road bottlenecks"