an ulceration, esp of the lips or lining of the oral cavity
He was suffering from canker sores in his mouth.
I have a lump on the inside of my lip and I'm positive it is a canker sore.
canker sore in American English
noun
Pathology
an ulceration of a mucous membrane, esp. of the mouth
Word origin
[1905–10]This word is first recorded in the period 1905–10. Other words that entered Englishat around the same time include: aspect ratio, jazz, persona, stabilizer, thiamine