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variant of megalo- (megalith); also the initial element in units of measure that are equal to one million of the units denoted by the base word (megahertz). Symbol: M.
Also, especially before a vowel, meg-.
Origin of mega-
combining form representing Greek mégas large, great Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for mega


(slang) extremely good, great, or successful
Word Origin
C20: probably independent use of mega-


combining form
denoting 106: megawatt, M
(in computer technology) denoting 220 (1 048 576): megabyte
large or great: megalith
(informal) great in importance or amount: megastar
Word Origin
from Greek megas huge, powerful
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
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Word Origin and History for mega


before vowels meg-, word-forming element often meaning "large, great," but in precise scientific language "one million" (megaton, megawatt, etc.), from Greek megas "great, large, vast, big, high, tall; mighty, important" (fem. megale), from PIE *meg- "great" (cf. Latin magnus, Old English micel; see mickle). Mega began to be used alone as an adjective by 1982.

High-speed computer stores 2.5 megabits [headline in "Electronics" magazine, Oct. 1, 1957]

Online Etymology Dictionary, © 2010 Douglas Harper
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mega in Medicine

mega- pref.

  1. Large: megacephaly.

  2. One million (106): megahertz.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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mega in Science
  1. A prefix that means:

  2. Large, as in megadose, a large dose.

  3. One million, as in megahertz, one million hertz.

  4. 220 (that is, 1,048,576), which is the power of 2 closest to a million, as in megabyte.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Slang definitions & phrases for mega



Much: I got mega homework tonight


Very: This dude is mega gross (1980s+ Students & teenagers)



A very large specimen, quantity, etc, of what is indicated: megabitch/ megablitz/ mega-cost/ megafame/ megagreed/ megahopes/ megamodel/ mega-travel (1981+)

The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D.
Copyright (C) 2007 by HarperCollins Publishers.
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