undergirt

Boyd’s Bible Dictionary:

A primitive way of keeping the hull of a ship from opening by passing a cable tightly around it

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 27:1717Which when they had taken up, they used helps, undergirding the ship; and, fearing lest they should fall into the quicksands, strake sail, and so were driven. (Acts 27:17)). It is called in the navy frapping.

Strong’s Dictionary of Greek Words:

Greek:
ὑποζώννυμι
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)
KJV Usage:
undergirt