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[sin-uh-ster] /ˈsɪn ə stər/
threatening or portending evil, harm, or trouble; ominous:
a sinister remark.
bad, evil, base, or wicked; fell:
his sinister purposes.
unfortunate; disastrous; unfavorable:
a sinister accident.
of or on the left side; left.
Heraldry. noting the side of an escutcheon or achievement of arms that is to the left of the bearer (opposed to dexter).
Origin of sinister
late Middle English
1375-1425; late Middle English < Latin: on the left hand or side, hence unfavorable, injurious
Related forms
sinisterly, adverb
sinisterness, noun
unsinister, adjective
unsinisterly, adverb
unsinisterness, noun
1. inauspicious, portentous. 3. unlucky.
1. benign. 3. favorable. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for sinister
Contemporary Examples
Historical Examples
  • We do it in a sinister sense more often than by way of helpfulness.

  • The sinister association of ideas made Mary shudder, but she said no more.

    Within the Law Marvin Dana
  • The voice of the older man came with a sinister force and saturnine.

    Within the Law Marvin Dana
  • Dick, too, winced under the pain of this meeting with his father in a situation so sinister.

    Within the Law Marvin Dana
  • There was a sinister thread in that flowing note, and suddenly Dick remembered.

    The Rock of Chickamauga Joseph A. Altsheler
British Dictionary definitions for sinister


threatening or suggesting evil or harm; ominous: a sinister glance
evil or treacherous, esp in a mysterious way
(usually postpositive) (heraldry) of, on, or starting from the left side from the bearer's point of view and therefore on the spectator's right
(archaic) located on the left side
(archaic) (of signs, omens, etc) unfavourable
Compare dexter1
Derived Forms
sinisterly, adverb
sinisterness, noun
Word Origin
C15: from Latin sinister on the left-hand side, considered by Roman augurs to be the unlucky one
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for sinister

early 15c., "prompted by malice or ill-will, intending to mislead," from Old French senestre, sinistre "contrary, false; unfavorable; to the left" (14c.), from Latin sinister "left, on the left side" (opposite of dexter), of uncertain origin. Perhaps meaning properly "the slower or weaker hand" [Tucker], but Klein and Buck suggest it's a euphemism (see left (adj.)) connected with the root of Sanskrit saniyan "more useful, more advantageous." With contrastive or comparative suffix -ter, as in dexter (see dexterity).

The Latin word was used in augury in the sense of "unlucky, unfavorable" (omens, especially bird flights, seen on the left hand were regarded as portending misfortune), and thus sinister acquired a sense of "harmful, unfavorable, adverse." This was from Greek influence, reflecting the early Greek practice of facing north when observing omens. In genuine Roman auspices, the augurs faced south and left was favorable. Thus sinister also retained a secondary sense in Latin of "favorable, auspicious, fortunate, lucky."

Meaning "evil" is from late 15c. Used in heraldry from 1560s to indicate "left, to the left." Bend (not "bar") sinister in heraldry indicates illegitimacy and preserves the literal sense of "on or from the left side" (though in heraldry this is from the view of the bearer of the shield, not the observer of it).

Online Etymology Dictionary, © 2010 Douglas Harper
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sinister in Medicine

sinister sin·is·ter (sĭn'ĭ-stər)

  1. Presaging trouble; ominous.

  2. On the left side; left.

sin'is·ter·ly adv.
sin'is·ter·ness n.
The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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