Dictionary.com
Thesaurus.com
Jump To:
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.

See Examples For:

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

Its Basic programming language and DOS operating system weren’t innovative in the market—but became standards.

From Barron's Mar. 13, 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

Most operating systems have a text editor: DOS has edit, Windows has Notepad, MacOS has SimpleText.

From Debian GNU/Linux : Guide to Installation and Usage by John Goerzen

We also computed the direction of selection, DoS, which is positive with adaptive selection, zero under neutrality and negative when weakly deleterious or new nearly neutral mutations are segregating.

From Nature Feb. 8, 2012

Unlike , DoS takes into account the constraints inferred from the current polymorphism, distinguishing negative, neutral and adaptive selection.

From Nature Feb. 8, 2012

Vocabulary.com logo
by dictionary.com

Dictionary.com's Learning Companion

Go beyond just looking up words.
Remember them forever with VocabTrainer.

Start training