Wiktionary
n. The process of transferring cargo or fuel off of a sunken or grounded ship, making it easier to refloat. vb. (present participle of lighter English)
Wikipedia
Lightering (also called lighterage) is the process of transferring cargo between vessels of different sizes, usually between a barge and a bulker or oil tanker. Lightering is undertaken to reduce a vessel's draft in order to enter port facilities which cannot accept very large ocean-going vessels. Lightering can also refer to the use of a lighter barge for any form of short-distance transport, such as to bring railroad cars across a river. In addition, lightering can refer to the process of removing oil or other hazardous chemicals from a compromised vessel to another vessel to prevent oil from spilling into the surrounding waters.
Usage examples of "lightering".
The problem forced Sal to go through the trouble and added expense of lightering down her cargo, rather than landing in the port where two other Venerian vessels took advantage of the relaxing of the Federation's embargo on trade with its Near Space colonies.