a rough surface made of dried blood that forms over a cut or broken skin while it is healing

Compare: scar noun

a skin disease in animals, especially sheep

The animals were all in a poor condition and were suffering from sheep scab.

an insulting word for a person who continues working while other people in the same organization are on strike

to form a scab or become covered by a scab

The wound has scabbed over. 伤口上长了疥疮。