The definition of sinister is a person or thing that threatens harm or misfortune.(adjective)
See sinister in Webster's New World College Dictionary
Origin: 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
See sinister in American Heritage Dictionary 4
Origin: Middle English sinistre, unfavorable
Origin: , from Old French
Origin: , from Latin sinister, on the left, unlucky.
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