OMC 

Oh My Cthulhu - a replacement for "Oh My God" (aka "omg") for those who prefer one (for whatever reason, including you're not religious or you're too religious to feel comfy using "god"). OMC evokes the great chaotic deity from Lovecraftian lore. Often used humorously.

Additional exclamation replacements include:
"Cthulhu's spawn!" instead of: "Jesus Christ!"
"Praise the Chaotic One" instead of: "Praise the Lord"

anyway you'd use omg
"OMC, what was that sound?"

OMC by CuteyPatootey April 3, 2015

omc 

OTARA MILLIONIARS CLUB
An R and B group that started in otara, Auckland,New Zealand.Then moved on to the States.Paul Fueamana(bad spelling?)and co.His brother(Phil) just died Circa March 2005 rip.Best known for 'How Bizarre'.

Wow what ever happened to OMC?

omc by Thrushbeard March 9, 2005

OMC 

Basically a replacement for OMG, but instead of god at the end I thought a more iconic figure:Charizard.
The meaning is can range from surprise to 'that's just awesome'.

Everybody I just won the lottery, OMC!
OMC, that guy just jumped off a bridge!

OMC by HippoPenguin October 4, 2010

OMC 

O.M.C=Over mature child
Used to poke fun at someone who has a mature face but likes things normally associated with children or acts childishly.

Ben: Glenn, stop being so lame and childish, stop telling me about your adventures about you and your power ranger figurines, for god's sake, you are already 21.

Glenn: Mind your own business.

Ben:Whatever, how OMC can you get?

OMC by Spentaz September 4, 2009

OMC 

To hang out with friends for a short period of time, usually for 45 - 90 minutes.
It is looked at as a bad thing to do, not very proper.

"yo can you chill today"
"I dunno, if anything it will be an OMC"

OMC by Schnitzeled May 20, 2009

OMC 

Off my charts

Rate~omc

OMC by Phoebe Simone April 10, 2015

OMC 

Acronym of Oh My Chad, a variation of oh my god, originating in the Disney channel series Sonny With a Chance. Commonly used by screaming fangirls.

Person 1: Do you like the movie Starstruck?

Person 2: OMC, it's amazing!

OMC by thequeenofallruralsuburbia August 10, 2010