A coat of arms ornamentation that is supposedly a sign of illegitimacy. The phrase, which has appeared in the works of novelists Laurence Sterne and Sir Walter Scott, implies a “bar” that prevents the person from a legitimate claim or inheritance, while “sinister” (the heraldic term for a coat of arms' left side) sounds menacing. Although the idea of a bar sinister on an illegitimate person's shield entered popular speech more than two centuries ago, that's not heraldically correct. A patterned border around a shield was the British heraldry way of indicating bastardy, and if you want to be even more technical, a thin diagonal line that does not touch the edges of the shield is a “baton,” not a “bar.” However, people rarely check with the College of Arms before using words and phrases.