mattress /ˈmætɹɪs/noun 3verb 1forms 3 noun3 •A pad on which a person can recline and sleep, usually having an inner section of coiled springs covered with foam or other cushioning material then enclosed with cloth fabric. •A form of retaining wall used to support foundations or an embankment •A form of lagging, in particular for boilers.Spun glass mattresses are used for lagging the boiler, which has three Ross pop safety valves on the front ring. — 1941 verb1 •To cover with a thick layer, like a mattress; to blanket.A comfortable litter of pine needles had mattressed the ground and spreading branches had been a canopy overhead. — 1997 formsmattressed · mattressing · mattresses