Mega

1.
variant of (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.
/ˈmɛɡə/
adjective
1.
(slang) extremely good, great, or successful
combining form
1.
denoting 106: megawatt, M
2.
(in computer technology) denoting 220 (1 048 576): megabyte
3.
large or great: megalith
4.
(informal) great in importance or amount: megastar

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]

mega- pref.

mega-

adjective

Much: I got mega homework tonight

adverb

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

-prefix

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