Definitions
1.AdjectiveInauspicious, ominous, unlucky, illegitimate (as in bar sinister).
2.AdjectiveEvil or seemingly evil; indicating lurking danger or harm."sinister influences; the sinister atmosphere of the crypt"
3.AdjectiveOf the left side.
4.AdjectiveOn the left side of a shield from the wearer's standpoint, and the right side to the viewer.
5.AdjectiveWrong, as springing from indirection or obliquity; perverse; dishonest.