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auto

1 American  
[aw-toh] / ˈɔ toʊ /

noun

plural

autos

  1. automobile.

adjective

  1. of or relating to automobiles.

    an auto salesman; auto detailing.
auto- 2 American  

  1. a combining form meaning “self,” “same,” “spontaneous,” used in the formation of compound words.

    autograph, autodidact.
auto- 3 American  

  1. a combining form representing automobile in compound words.

    autocade.
auto- 4 American  

  1. a combining form representing automatic in compound words: autoalarm; autofeed; autofocus . Sometimes also taken as an adjective.

    auto enlarger; auto stop control; auto dialer.
auto. 5 American  

abbreviation

  1. automatic.

  2. automobile.

  3. automotive.

auto 1 British  
/ ˈɔːtəʊ /

noun

    1. short for automobile

    2. ( as modifier )

      auto parts

  2. informal short for autorickshaw

"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
auto- 2 British  

combining form

  1. self; same; of or by the same one

    autobiography

  2. acting from or occurring within; self-caused

    autohypnosis

  3. self-propelling; automatic

    automobile
"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 auto1

An Americanism dating back to 1895–1900; by shortening

Origin of auto-2

< Greek, combining form of autós self

Origin of auto-3

see origin at auto

Explanation

An auto is a car. If you drive your auto too fast, you might get a speeding ticket. The word auto is an informal, shortened form of automobile. You're most likely to hear the word auto when someone's talking about insurance, auto parts, or the auto industry. Automobile was originally a French word, formed from the Greek autos, or "self," and the French mobile, "moving."

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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.

Find insight on commercial vessels, Air Canada and more in the latest Market Talks covering the auto and transport sector.

From The Wall Street Journal • Apr. 17, 2026

Semiconductor stocks face diverging fortunes as a weak auto market, projected to decline 2% in production, contrasts with strong data-center demand.

From Barron's • Apr. 17, 2026

The concerns about private credit broadly were initially sparked by allegations of credit fraud that surfaced in the collapse of two auto companies.

From The Wall Street Journal • Apr. 17, 2026

As shares of the auto maker tumbled on Friday, shares of one of its partners were rising.

From Barron's • Apr. 17, 2026

It's her car aren't you proud of your little sister owns first auto in town Herbert his present.

From "The Sound and the Fury" by William Faulkner

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.