the GNU version of the Collaborative International Dictionary of English
adj. Not decked; unadorned.
adj. Not having a deck.
The Century Dictionary and Cyclopedia
Not decked; not adorned.
Not having a deck: as, an undecked vessel or barge.
Word Usage
"Trelawny wrote: "Shelley's was an undecked open boat, schooner rigged and being undecked she would have sunk in two minutes" (letter to The Times, London, 3 January 1876)."