A spool is a cylinder with a rim at each end, designed for winding thread, wire, rope, or similar materials around its middle section. Picture the wooden or plastic spools that sewing thread comes wrapped around. The raised edges on both ends keep the thread from slipping off as it winds around the center.

Spools organize materials that would otherwise tangle into hopeless knots. Fishing line spooled neatly on a reel can be cast out smoothly and reeled back in without snarls. Film used to come on spools before digital cameras, wound carefully so projectors could display movies frame by frame. In factories, enormous spools hold cables, wire, and industrial materials.

The word also works as a verb: when you spool something, you wind it onto a spool. Your printer might spool documents, meaning it lines them up in memory before printing. Computer programmers borrowed this term from the way early computers handled print jobs, and the name stuck even after the technology changed.