Definitions
1.adjectiveInauspicious, ominous, unlucky, illegitimate (as in bar sinister).
2.adjectiveEvil or seemingly evil; indicating lurking danger or harm."sinister influences"
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.