Stop-out
Automatic closure of open positions when margin level falls below the broker's minimum.
Different brokers, different thresholds: 20%, 50%, 100% of required margin. Biggest losers close first. Stop-out isn't a 'bad tick' - it's a position-sizing failure compounded by refusing to cut the loss early.
Related
Learn to actually use Stop-out.
Definitions are the easy part. The free first five modules put this on a real chart and make you do the work. No card required.