sin·is·ter / ˈsinistər/ • adj. 1. giving the impression that something harmful or evil is happening or will happen: there was something sinister about that murmuring voice. ∎ wicked or criminal.2. archaic & Heraldry of, on, or toward the left-hand side (in a coat of arms, from the bearer's point of view, i.e., the right as it is depicted). The opposite of dexter1 .DERIVATIVES: sin·is·ter·ly adv.sin·is·ter·ness n.
In heraldry, of, on, or towards the left-hand side (in a coat of arms, from the bearer's point of view, i.e. the right as it is depicted); the opposite of dexter.
See also bend sinister.