bottleneck (Noun) — A narrowing that reduces the flow through a channel.
bottleneck (Noun) — The narrow part of a bottle near the top.
bottleneck (Verb) — Slow down or impede by creating an obstruction. ex. "His laziness has bottlenecked our efforts to reform the system"
bottleneck (Verb) — Become narrow, like a bottleneck. ex. "Right by the bridge, the road bottlenecks"