n.1. a. A narrow or obstructed section, as of a highway or a pipeline.
b. A point or an area of traffic congestion.
2. A hindrance to progress or production.
3. The narrow part of a bottle near the top.
4. Music A style of guitar playing in which an object, such as a piece of glass or metal, is passed across the strings to achieve a gliding sound.
5. Biology An abrupt and severe reduction in the number of individuals during the history of a species of a population, often resulting in the loss of diversity from the gene pool.