adj. 25B6; adjective
there was a sinister undertone in his words : MENACING, threatening, ominous, forbidding, baleful, frightening, alarming, disturbing, disquieting, dark, black; formal minatory; poetic/literary direful.
a sinister motive : EVIL, wicked, criminal, corrupt, nefarious, villainous, base, vile, malevolent, malicious; informal shady.
innocent.