Boyd’s Bible Dictionary:
A primitive way of keeping the hull of a ship from opening by passing a cable tightly around it
The ship in which Paul sailed from Crete to Italy was undergirded (Acts 27:17).
Concise Bible Dictionary:
The binding of either ropes or chains round a ship in bad weather, to keep it from parting asunder in consequence of its being old or because of its imperfect construction (Acts 27:17). It is called in the navy frapping.
Strong’s Dictionary of Greek Words:
Transliteration:
hupozonnumi
Phonic:
hoop-od-zone’-noo-mee
Meaning:
from 5259 and 2224; to gird under, i.e. frap (a vessel with cables across the keel, sides and deck)