kapok Definition

a massive tropical deciduous tree (Ceiba pentandra) of the silk-cotton family that has a trunk with short, sharp prickles, a buttressed base, and porous lightweight wood and that bears large seed pods containing numerous silky fibers

a mass of silky fibers that surrounds the seeds of the kapok tree and are used especially as a filling for mattresses, pillows, life preservers, and sleeping bags and as insulation