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sin·is·ter (sĭnĭ-stər)
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adj.
1.
a. Suggesting or threatening harm or evil: a sinister smile.
b. Causing or intending harm or evil; wicked: a sinister conspiracy.
2.
a. Portending misfortune or disaster; ominous: sinister storm clouds.
b. Attended by or causing misfortune or disaster: "The day has passed without any sinister accident" (John Quincy Adams).
3.
a. Archaic On the left side; left.
b. Heraldry Situated on or being the side of a shield on the wearer's left and the observer's right.
[Middle English sinistre, unfavorable, from Old French, from Latin sinister, on the left, unlucky.]
sinis·ter·ly adv.
sinis·ter·ness n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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