IPA: /ʌnˈdɛkt/
KK: /ʌnˈdɛkt/
Describing a ship or boat that does not have a deck, or something that is not decorated or ornamented.
The old ship was left undecked, revealing its bare structure.
Undecked is formed from "un-" (meaning not) and "deck" (from Old English *decc*, meaning to cover or adorn). The word means not covered or adorned, particularly in the context of a ship that is not fitted out with sails or rigging.
Think of 'not' ('un-') covering or adorning something ('deck') — that's why undecked means not adorned or covered.