canker

Concise Bible Dictionary:

The word of those who err from the truth eats like a “gangrene” which consumes the flesh. Such teaching saps the vitals of Christianity (2 Tim. 2:17).
Gangrene of the Lung

Strong’s Dictionary of Greek Words:

Greek:
γάγγραινα
Transliteration:
gaggraina
Phonic:
gang’-grahee-nah
Meaning:
from γραίνω (to gnaw); an ulcer ("gangrene")
KJV Usage:
canker