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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).
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. 2014.
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Examples for sinister
  • sinister barrier is a science fiction novel by author eric frank russell.
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
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Word Origin and History for sinister
1411, "prompted by malice or ill-will," from O.Fr. sinistre "contrary, unfavorable, to the left," from L. sinister "left, on the left side" (opposite of dexter), perhaps from base *sen- and meaning prop. "the slower or weaker hand" [Tucker], but Buck suggests it's a euphemism (see left), connected with the root of Skt. saniyan "more useful, more advantageous." The L. 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 Gk. influence, reflecting the early Gk. practice of facing north when observing omens; in genuine Roman auspices, the left was favorable. Bend (not "bar") sinister in heraldry indicates illegitimacy and preserves the lit. sense of "on the left side."
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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