What does sinister mean?

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From our dictionary:

sin•is•ter

Pronunciation: (sin'u-stur), [key]
adj.
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. Heraldry.noting the side of an escutcheon or achievement of arms that is to the left of the bearer (opposed to dexter).