an ulceration of a mucous membrane, especially of the mouth.
Origin of canker sore
First recorded in 1905–10
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
A small painful ulcer of the mucous membrane of the mouth; an aphtha.aphthous stomatitis recurrent aphthous ulcers ulcerative stomatitis
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.