If a piece of clothing or material pills, it develops small balls of threads on its surface.

(衣服或布料)起球粒，起纤维绒球

Fabrics with a large number of loose fibers have a higher tendency to pill.

含有大量松散纤维的织物更容易起球。

a small ball of threads that develops on the surface of clothes or material

(衣服或布料上的)球粒，纤维绒球

She sat there sulking and picking the pills off her sweater.

她坐在那里生闷气，一个劲地拽着毛衣上的绒球。