[UNDER-1 5 b. Cf. Du. onderdek, G. unterdeck, Da. underdæk, Sw. -däck.] The lower deck of a vessel. Also attrib.
1826. Scott, Provinc. Antiq. Scot., 73. Each inhabitable space was crowded like the underdeck of a ship.
1867. Smyth, Sailors Word-bk., 705. Under deck, the floor of a cabin, or tween decks.
1872. Talmage, Serm., 43. Allow your appetites and passions only an under-deck passage.