In the context of naval terminology, Jack explains the term "devil," which refers to the challenging seam between the deck-planking and the timbers of a ship. This seam poses a significant difficulty for caulkers, making it a frustrating point of labor. The full expression, "the devil to pay and no pitch hot," signifies a daunting task that must be tackled despite the lack of adequate resources or tools. It illustrates the theme of facing tough challenges without necessary provisions.

This metaphor is apt for situations where one confronts arduous tasks and must find a way to accomplish them, even when the odds are stacked against them. The struggle inherent in tackling such 'devilish' problems reflects broader themes of perseverance and resilience, showcasing the complexities of maritime life in O'Brian's narrative. The term captures the essence of difficult decisions and the arduous nature of the work that seafarers undertake.