sin ‧ is ‧ ter /ˈsɪnəstə, ˈsɪnɪstə $ -ər/ BrE AmE adjective
[ Date: 1400-1500 ; Language: Old French ; Origin: sinistre , from Latin sinister 'left-handed, unlucky' ]
making you feel that something evil, dangerous, or illegal is happening or will happen
there 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