Scab

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, especially. When it appears on sheep.
4. A disease of potatoes producing pits in their surface, caused by a minute fungus (Tiburcinia scabies).
5. A slight iregular 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.
Origin: OE. Scab, scabbe, shabbe; cf. AS. Scaeb, sceabb, scebb, Dan. & Sw. Skab, and also L. Scabies, tr. Scabere to scratch, akin to E. Shave. See Shave, and cf. Shab, Shabby.