American Tract Society Bible Dictionary
Passing a cable several times under and around a ship and tightening it on deck, to prevent the working and parting of the timbers and planks in a gale, Acts 27:17 . The process is called frapping, and has been resorted to in various instances in modern times.
These files are public domain and are a derivative of the topics are from American Tract Society Bible Dictionary published in 1859.
Rand, W. W. Entry for 'Undergird'. American Tract Society Bible Dictionary. https://www.studylight.org/dictionaries/eng/ats/u/undergird.html. 1859.