In heraldry, the left-hand side of a shield. As shields are supposed to be carried in front of the person, the sinister side is that which covers the bearer's left side. Therefore, it lies to the spectator's right.
Related term(s): Heraldry; Points of the Escutcheon; Dexter; Base (Heraldry); Ordinary; Arms (Heraldry)
Source information: Wilhelm, Thomas. A Military Dictionary and Gazetteer. Philadelphia: L.R. Hamersly & Co., 1881. 535.