- sinister [sin′is tər]adj.[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]1.a) Archaic on, to, or toward the left-hand side; leftb) Heraldry on the left side of a shield (the right as seen by the viewer): opposed to DEXTER2. 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]sinisterlyadv.sinisternessn.SYN.- SINISTER, in this connection, applies to that which can be interpreted as presaging imminent danger or evil [a sinister smile ]; BALEFUL refers to that which is inevitably deadly, destructive, pernicious, etc. [a baleful influence ]; MALIGN is applied to that which is regarded as having an inherent tendency toward evil or destruction [a malign doctrine ]
English World dictionary. V. Neufeldt. 2014.