What is the meaning of Mattress?

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.

To cover with a thick layer, like a mattress; to blanket.

Source: wiktionary.org