a fabric case filled with resilient material, e.g. feathers, foam rubber, or an arrangement of coiled springs, used as, or on, a bed
a mass of interwoven brush and poles to protect a bank from erosion, or a similar mass serving as a foundation in soft ground
a concrete slab or raft used as a foundation or footing
[Middle English materas via Old French from Arabic maṭrah place where something is thrown]