Meaning of sinister

sin•is•ter

1. threatening or portending evil, harm, or trouble; ominous: a sinister remark.
2. bad, evil, base, or wicked; fell: his sinister purposes.
3. unfortunate; disastrous; unfavorable: a sinister accident.
4. of or on the left side; left.
5. noting the side of an escutcheon or achievement of arms that is to the left of the bearer (opposed to dexter).