1. a structure that projects over the side of a ship or boat; specif.,
b. an air chamber built into the gunwale of a canoe
2. a short, winglike piece attached to the hull of a seaplane just above water level to give stability in the water
Webster’s New World College Dictionary, Fourth Edition, compiled by the
editors of Webster’s New World Dictionaries. Copyright © 2010 by Houghton
Mifflin Harcourt. Published by Houghton Mifflin Harcourt. All rights reserved.
Word origin of 'sponson'
altered < ? expansion
: orig. applied to the platforms on each side of a steamer's paddle wheels