to stubbornly focus on an insoluble problem or get caught in a dead-end way of thinking

to be extremely diligent in one's studies, making use of every spare moment to read and learn

to waste time on an insoluble or insignificant problem, or to get stuck in a dead end by over-analyzing trivial details

A variety of long, tapered chili pepper resembling a cow's horn, typically used for its mild to moderate heat.