- an acute, usually fatal, infectious disease of young cattle and sheep, caused by a bacterium (esp. Clostridium chauvoei) and characterized by swelling and blackening of infected muscle tissue
- a disease of beets and related plants caused by a fungus (Phoma betae)
- a disease of potatoes caused by a bacterium (Erwinia atroseptica)
- Informal a gambler who cheats
- Brit. a strikebreaker
- An infectious, usually fatal bacterial disease of cattle and sometimes of sheep, goats, and swine, caused by Clostridium chauvoei and characterized by gas-containing swellings in the musculature.
- 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.
- One who cheats at cards; a cardsharp.
- Chiefly British A worker who is opposed to trade unions; a scab.
(countable and uncountable, plural blacklegs)
- Relating to a scab worker.
- The blackleg workers entered under cover of darkness.