[mat.tress] n [ME materas, fr. OF, fr. Ar matrah place where something is thrown] (14c) 1 a: a fabric case filled with resilient material (as cotton, hair, feathers, foam rubber, or an arrangement of coiled springs) used either alone as a bed or on a bedstead b: an inflatable airtight sack for use as a mattress
2: a device (as of interwoven brush and poles) used to protect a shoreline, bank, or streambed from erosion