The narrow portion that forms the pouring spout of a bottle; the neck of a bottle.
In traffic, any narrowing of the road, especially resulting in a delay.
(by extension) The part of a process that is too slow or cumbersome.
It is easy to create entries; processing the paperwork is the bottleneck.
To slow by causing a bottleneck.
The merge bottlenecked the traffic every morning.
To form a bottleneck.
The traffic bottlenecked at the merge every morning.