adjective

1. 1. Archaic on, to, or toward the left-hand side; left
   2. Heraldry on the left side of a shield (the right as seen by the viewer)
2. threatening harm, evil, or misfortune; ominous; portentous sinister storm clouds
3. wicked, evil, or dishonest, esp. in some dark, mysterious way a sinister plot
4. most unfavorable or unfortunate; disastrous met a sinister fate

Etymology: ME sinistre < L sinister, left-hand, or unlucky (side), orig. lucky (side) < IE base *sene-, to prepare, achieve > Sans sánīyān, more favorable: early Roman augurs faced south, with the east (lucky side) to the left, but the Greeks (followed by later Romans) faced north