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ultra

1 American  
[uhl-truh] / ˈʌl trə /

adjective

  1. going beyond what is usual or ordinary; excessive; extreme.

noun

  1. an extremist, as in politics, religion, fashion, etc.

  2. Military. Ultra, the British code name for intelligence gathered by decrypting German wireless communications enciphered on the Enigma machine during World War II.

ultra- 2 American  

  1. a prefix occurring originally in loanwords from Latin, with the basic meaning “on the far side of, beyond.” In relation to the base to which it is prefixed, ultra- has the senses “located beyond, on the far side of ” (ultramontane; ultraviolet ), “carrying to the furthest degree possible, on the fringe of ” (ultraleft; ultramodern ), “extremely” (ultralight ); nouns to which it is added denote, in general, objects, properties, phenomena, etc., that surpass customary norms, or instruments designed to produce or deal with such things (ultramicroscope; ultrasound; ultrastructure ).

ultra 1 British  
/ ˈʌltrə /

adjective

  1. extreme or immoderate, esp in beliefs or opinions

"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

noun

  1. an extremist

"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
ultra- 2 British  

prefix

  1. beyond or surpassing a specified extent, range, or limit

    ultramicroscopic

  2. extreme or extremely

    ultramodern
"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 ultra1

Independent use of ultra-, or shortening of words prefixed with it

Origin of ultra-2

From Latin ultrā (adverb and preposition) “on the far side,” derivative of ulter (unrecorded) “located beyond”

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.

During the 1980s, researchers studying ultra thin conductors at extremely low temperatures made a surprising discovery.

From Science Daily

The team focused on ultra thin films made from two elements, tellurium and selenium.

From Science Daily

These ultra thin materials are known to behave very differently from their thicker, three-dimensional versions.

From Science Daily

The new metasurface takes the form of an ultra thin chip covered with tiny structures that are smaller than the wavelength of light itself.

From Science Daily

The company significantly expanded its offerings in 2025 “to give members access to investment tools traditionally reserved for the ultra wealthy,” Noto said.

From Barron's

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.