[UNDER-1 5 b. Cf. Du. onderdek, G. unterdeck, Da. underdæk, Sw. -däck.] The lower deck of a vessel. Also attrib.

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1826.  Scott, Provinc. Antiq. Scot., 73. Each inhabitable space was crowded like the underdeck of a ship.

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1867.  Smyth, Sailor’s Word-bk., 705. Under deck, the floor of a cabin, or ’tween decks.

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1872.  Talmage, Serm., 43. Allow your appetites and passions only an under-deck passage.

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