blackleg

(blăkˈlĕgˌ)

1. An infectious, usually fatal bacterial disease of cattle and sometimes of sheep, goats, and swine, caused by Clostridium chauvoe and characterized by gas-containing swellings in the musculature.
2. A bacterial or fungal disease of certain plants, such as the cabbage and potato, that causes the stems to turn black at the soil line.
3. One who cheats at cards; a cardsharp.
4. Chiefly British A worker who is opposed to trade unions; a scab.