scab

An incrustation over a sore, wound, vesicle, or pustule, formed during healing.

(slang, offensive) A worker who acts against trade union policies; any picket crosser (strikebreaker), and especially one with devotion to union busting.

Any of several different diseases of potatoes producing pits and other damage on their surface, caused by streptomyces bacteria (but formerly believed to be caused by a fungus).

Common scab, a relatively harmless variety of scab (potato disease) caused by Streptomyces scabies.

Any one of various more or less destructive fungal diseases that attack cultivated plants, forming dark-colored crustlike spots.

The mange, especially when it appears on sheep.

A mean, dirty, paltry fellow.

A slight irregular protuberance which defaces the surface of a casting, caused by the breaking away of a part of the mold.

(informal, no longer used) The scabies.

To become covered by a scab or scabs.

To act as a strikebreaker.

(UK, informal) To beg (for), to cadge or bum.

To form into scabs and be shed, as damaged or diseased skin.

To remove part of a surface (from).