Any of several worms of the phylum Nematoda, having unsegmented, cylindrical bodies, often narrowing at each end, and including parasitic forms such as the hookworm and pinworm.

• 线虫线虫纲动物的任何一种小虫，身体不分节，呈柱状，两头稍尖，包括钩虫和蛲虫一样的寄生虫