1. a. a narrow route b. a point of traffic congestion 2. a. someone or something that retards or halts free movement and progress b.impasse c. a dramatic reduction in the size of a population (as of a species) that results in a decrease in genetic variation 3. a style of guitar playing in which glissando effects are produced by sliding an object (as a knife blade or the neck of a bottle) along the strings — called also bottleneck guitar