Scab

1. An incrustation over a sore, wound, vesicle, or pustule, formed by the drying up of the discharge from the diseased part.
2. The itch in man; also, the scurvy.
3. The mange, esp. when it appears on sheep.
4. A disease of potatoes producing pits in their surface, caused by a minute fungus (Tiburcinia Scabies).
5. (Founding) A slight irregular protuberance which defaces the surface of a casting, caused by the breaking away of a part of the mold.
6. A mean, dirty, paltry fellow.
7. A nickname for a workman who engages for lower wages than are fixed by the trades unions; also, for one who takes the place of a workman on a strike.
8. (Bot.) Any one of various more or less destructive fungus diseases attacking cultivated plants, and usually forming dark-colored crustlike spots.

1. To become covered with a scab; as, the wound scabbed over.
2. to take the place of a striking worker.