scab
nounA crust discharged from and covering a healing wound.
nounScabies or mange in domestic animals or livestock, especially sheep.
nounAny of various plant diseases caused by fungi or bacteria and resulting in crustlike spots on fruit, leaves, or roots.
nounThe spots caused by such a disease.
nounA person regarded as contemptible.
nounA worker who refuses membership in a labor union.
nounAn employee who works while others are on strike; a strikebreaker.
nounA person hired to replace a striking worker.