tad.mor is a proper name for a place described as built in the wilderness.

The term occurs as a proper noun naming a place described as built in the wilderness in both supplied verses.

1. Place named in building accounts · dominant

   In 1 Kings 9:18, the proper-noun form occurs in a list of places built, and the APB renders the clause "Tadmor in the wilderness in the land." In 2 Chronicles 8:4, the same proper-noun use names the place built in the wilderness; the APB renders "He built Tadmor in the wilderness."

   1 Kings 9:182 Chronicles 8:4

In the Anselm Project Bible: The APB presents the term as "Tadmor" in both verses, within statements about building in the wilderness. It confirms the place-name setting rather than supplying a lexical definition.