Definitions

1. noun

a chronic and often painful sore, especially on the mouth or gums; a festering sore or abscess; a moral or mental defect or corruption

“The infection caused a painful canker on his lip.”

2. noun

a worm or grub that eats the bark of trees, especially the cankerworm or the lilac borer

“The canker in the oak tree was causing significant damage to the surrounding foliage.”

3. verb

to eat away or corrode, especially the bark of a tree

“The canker was eating away at the base of the tree trunk.”