The term 'bar sinister' refers to a mark on an escutcheon (a shield) that denotes illegitimacy or dishonor. The opposite of this term could be 'bar dexter,' which refers to an honorable or legitimate mark on an escutcheon. Another antonym of bar sinister could be 'barry,' which is a heraldic term used to describe a shield that is divided into horizontal sections of two or more colors. In contrast, 'barless' is another antonym that indicates a shield without a horizontal bar or division. One could also consider 'bar erect' as an antonym to bar sinister, which means a vertical metal bar or rod often used for support or in construction.