n. pl. cal·lus·es
a. A localized thickening and enlargement of the horny layer of the skin. Also called callosity.
b. The hard bony tissue that develops around the ends of a fractured bone during healing.
a. Undifferentiated tissue that develops on or around an injured or cut plant surface or in tissue culture.
b. The hardened, sometimes sharp base of the spikelet of certain grasses.
intr.v. cal·lused, cal·lus·ing, cal·lus·es
To form or develop such hardened tissue. See Usage Note at callous.
[Latin, masculine of callum.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.