Canker (noun)

1. A sore or ulcer on the skin or mucous membrane.
2. A destructive disease of plants, typically characterized by the formation of cankers.
3. A source of corruption or decay; a moral or spiritual blight.

Origin:

Old english cencer, from cencen "cancer" (from latin cancer "crab"), later associated with canker "ulcer" (from old english canca "cancer, ulce.r")

Examples:

1. The canker on his lip was painful and unsightly.
2. The canker was caused by a bacterial infection.
3. The apple tree was affected by canker and had to be cut down.
4. The canker of corruption was eating away at the company from within.
5. The canker of greed and ambition was destroying the politician's reputation.