A gangrene or mortification which gradually spreads over the whole body (2 Timothy 2:17). In James 5:3 "cankered" means "rusted" (RSV) or tarnished.

CANKER, n.

1. A disease incident to trees, which causes the bark to rot and fall.

2. A popular name of certain small eroding ulcers in the mouth, particularly of children. They are generally covered with a whitish slough.

3. A virulent, corroding ulcer; or any thing that corrodes, corrupts or destroys.

Sacrilege may prove an eating canker.

And their word will eat as doth a canker. Tim. 2.

4. An eating, corroding, virulent humor; corrosion.

5. A kind of rose, the dog rose.

6. In farriery, a running thrush of the worst kind; a disease in horses feet, discharging a fetid matter from the cleft in the middle of the frog.

CANKER, v.i. To grow corrupt; to decay, or waste away by means of any noxious cause; to grow rusty, or to be oxydized, as a metal.