From Longman Dictionary of Contemporary Englishsinistersin‧is‧ter /ˈsɪnɪstə $ -ər/ ●○○ adjective BAD BEHAVIOUR OR ACTIONSmaking you feel that something evil, dangerous, or illegal is happening or will happenthere is something/nothing sinister about somebody/something There was something sinister about Mr Scott’s death. There is a sinister side to these events. He was a handsome man, in a sinister sort of way. a sinister atmosphere
Examples from the Corpus
sinister• The First Couple looks sleazy and careless but not necessarily sinister.• Her dark eyes and evil laugh made her seem sinister.• Daffy keeps reappearing to Richard as a ghost, unstoppably loquacious and with a joviality that turns increasingly sinister.• The man was dressed in a black suit and wore dark glasses. There was something sinister about him.• Their presence was all the more sinister amidst the approaching thunder of anticlericalism.• As I gazed on this incongruous tableau, however, the scene gradually took on a more sinister aspect.• Not even a sinister black cat, but a large and lazy-looking tabby.• A sinister figure lurked in the shadows.• There may be more sinister forces at work behind the scenes.• a sinister laugh• The drawing style is rough and abrasive, the heavy blacks underlining the sinister plotting of Silver and his renegades.• Some might say it's a sinister way to spend your time.Origin sinister (1400-1500) Old French sinistre, from Latin sinister “left-handed, unlucky” 