Having or characterized by a single slope or pitch: a lean-to roof; lean-to construction.
n. pl. lean-tos
1. A structure with a single-pitch roof that is attached to the side of a building as a wing or extension.
2. A shelter or shed having a roof with a single slope or pitch.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 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.