Sinister1. (a.) Evil; ominous; threatening.
2. (a.) Unlucky; inauspicious; disastrous; injurious; evil; -- the left being usually regarded as the unlucky side; as, sinister influences.
3. (a.) Wrong, as springing from indirection or obliquity; perverse; dishonest; corrupt; as, sinister aims.
4. (a.) Indicative of lurking evil or harm; boding covert danger; as, a sinister countenance.
Thesaurus Entries
adverse, amoral, antagonistic, apocalyptic, backhand, backhanded, bad, baleful, baneful, base, black, bodeful, boding, circuitous, conflicting, conscienceless, contrary, corrupt, corrupted, counter, counteractive, counterclockwise, criminal, crooked, dark, deflectional, detrimental, deviant, deviative, devious, diabolical, difficult, digressive, dire, disastrous, dishonest, dishonorable, divagational, divergent, doomful, doubtful, dreary, dubious, evasive, evil, evil-starred, excursive, fateful, felonious, fishy, foreboding, fraudulent, furtive, gloomy, hard, harmful, hostile, ill, ill-boding, ill-fated, ill-got, ill-gotten, ill-omened, ill-starred, immoral, improper, in opposition, inaccurate, inauspicious, indirect, inexpedient, inferior, inimical, insidious, invalid, larboard, left, left-hand, left-handed, left-wing, left-wingish, levorotatory, liberal, lowering, malefic, maleficent, malevolent, malicious, malign, malignant, menacing, minacious, minatory, miserable, near, nefarious, nigh, not easy, not kosher, oblique, of evil portent, ominous, opposed, opposing, opposite, peccant, pernicious, port, portending, portentous, questionable, radical, rigorous, rotten, shady, shameless, shifty, side, sidelong, sinful, sinistral, sinistrocerebral, sinistrocular, sinistrogyrate, sinistrorse, slippery, sneaky, somber, stressful, suspicious, threatening, treacherous, tricky, troublesome, troublous, trying, unconscienced, unconscientious, unconscionable, underhand, underhanded, unethical, unfavorable, unfortunate, unhealthy, unkind, unlucky, unpleasant, unprincipled, unpromising, unpropitious, unsavory, unscrupulous, unskillful, unstraightforward, untoward, vicious, villainous, wicked, without remorse, without shame, wretched, wrong