from
The Collaborative International Dictionary of English v.0.48
Scab \Scab\ (sk[a^]b), n. [OE. scab, scabbe, shabbe; cf. AS.
scaeb, sceabb, scebb, Dan. & Sw. skab, and also L. scabies,
fr. scabere to scratch, akin to E. shave. See {Shave}, and
cf. {Shab}, {Shabby}.]
1. An incrustation over a sore, wound, vesicle, or pustule,
formed by the drying up of the discharge from the diseased
part.
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2. The itch in man; also, the scurvy. [Colloq. or Obs.]
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3. The mange, esp. when it appears on sheep. --Chaucer.
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4. A disease of potatoes producing pits in their surface,
caused by a minute fungus ({Tiburcinia Scabies}).
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5. (Founding) A slight irregular protuberance which defaces
the surface of a casting, caused by the breaking away of a
part of the mold.
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6. A mean, dirty, paltry fellow. [Low] --Shak.
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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. [Cant]
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8. (Bot.) Any one of various more or less destructive fungus
diseases attacking cultivated plants, and usually forming
dark-colored crustlike spots.
[Webster 1913 Suppl.]