1. A large wave or swell of water.
2. A great swell, surge, or undulating mass, as of smoke or sound.
v. bil·lowed, bil·low·ing, bil·lows
1. To surge or roll in billows.
2. To swell out or bulge: sheets billowing in the breeze.
To cause to billow: wind that billowed the sails.
[From Old Norse bylgja, a wave; see bhelgh- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.