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Synonyms

DOS

1 American  
[daws, dos] / dɔs, dɒs /

noun

Computers.
  1. any of several single-user, command-driven operating systems for personal computers, especially MS DOS.


DOS 2 American  

abbreviation

  1. Department of State.


DoS 3 American  
[daws, dos, dee-oh-es] / dɔs, dɒs, ˈdiˌoʊˈɛs /

abbreviation

  1. Computers. denial-of-service.

    DoS protection for web servers.


DOS British  
/ dɒs /

acronym

  1. disk-operating system, often prefixed, as in MS-DOS and PC-DOS; a computer operating system

"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

Etymology

Origin of DOS

d(isk) o(perating) s(ystem)

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Since IBM chose an Intel CPU for its first PC in 1980, chips based around the x86 architecture have run Microsoft DOS and Windows PCs.

From Barron's • Jun. 2, 2026

Decart has two main business lines, the fastest-growing of which is known as the Decart Optimization Stack, or DOS.

From The Wall Street Journal • May 18, 2026

They called it JAWS, which stands for Job Access With Speech, but is also a playful reference to another DOS screen reader called Flipper, like the dolphin in an eponymous 1960s TV show.

From The Verge • Jul. 14, 2022

We’d still be staring at DOS prompts on monochrome screens.

From Seattle Times • Nov. 20, 2021

The antivirus directory has anti-virus programs for MS- DOS and Macintosh computers.

From Big Dummy's Guide to the Internet by Electronic Frontier Foundation

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