a. A usually rectangular pad of heavy cloth filled with soft material or an arrangement of coiled springs, used as or on a bed.
b. An airtight inflatable pad used as or on a bed or as a cushion.
2. A closely woven mat of brush and poles used to protect an embankment, a dike, or a dam from erosion.
[Middle English materas, mattresse, from Old French materas, from Old Italian materasso and from Medieval Latin matracium, both from Arabic maṭraḥ, place where something is thrown, mat, cushion, from ṭaraḥa, to throw; see ṭrḥ in the Appendix of Semitic roots.]
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