1. any of a number of deciduous trees having long flexible branches; cricket bat (made from the wood of a willow); machine with a spiked drum used for cleaning and loosening fibers (especially cotton and wool fibers). (weaving) loosen and clean fibers with a willow machine (especially wool and cotton fibers). willowwillow , n. [oe. wilowe, wilwe, as. wilig, welig; akin to od. wilge, d. wilg, lg. wilge. cf. willy.]