Definition of "inner tube" []

• A flexible, airtight hollow ring, usually made of rubber, that is inserted into the casing of a pneumatic tire for holding compressed air. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "We stayed at the Sport Hotel on the water in Tihany and I spent much of my time paddling around on an inner tube in the lake."