O'Brien 

Descended from the progenitor, Brian Boru - THE LAST GREAT HIGH KING OF IRELAND: the greatest military leader the country has ever known.

Two mottoes have been associated with the O'Brien clan: firstly, Vigueur de dessus: 'Strength from above' and secondly, 'Lamh laidir an uachtar' 'The strongest arm uppermost'

O'Brien by obrienwrite May 20, 2008

o dark thirty

Early in the morning before the sun is up.
Used to define when you must get up and go somewhere in the early hours of the morning between 1:30am and 5:30am.

a time in the am around the half hour mark.

"You're leaving tomarow? Will I get a chance to see you?"
"Nahh, we're taking off at o dark thirty. You won't be up yet."

o dark thirty by Cloudyjuicebox May 9, 2006

o shi 

Used when something bad is about to happen, but you don't have time to finish what you were saying because it happens and you are either dead, or otherwise unable to finish what you were saying.

(Online Chat Conversation)
Trevor: Brandon! Riley snuck over to my house and has a gun! I THINK HE IS GOING TO KILL ME!
Brandon: Are you serious?
Trevor: O SHI

o shi by Brandon Werner May 17, 2006

O'Donnell 

Beating someone else at something. Used in the same context as "Trumping" someone, only used as overpowering a Trump.

Person A: "You can't Trump Trump!"
Person B: "I just O'Donnelled your Trump!"

O'Donnell by Jordanface! January 3, 2008

O.S. The Best 

A common name used to describe someone that is very sensitive. "O" stands for "Over" and "S" stands for "Sensitive"

Guy 1: Did you see that guy cry in the movies?

Guy 2: Yea he is O.S. The Best

Guy 1: Exactly

O.S. The Best by Boinkin Her February 13, 2010

o'Dark 30 

A general term referring to any time between midnight and sunrise the next morning.

I don't want to get up at o'Dark 30 to go to the gym.

o'Dark 30 by 3atMyCak3 February 18, 2011

O'Tooled 

1)O'Tooled: Drunk. Hammered. Hungover. In referance to the British actor Peter O'Toole who stard in such films as Lawerance of Arabia, and was famous for off screen drinking binges.

2) O'Tooled: Denied. Rejected on a regular basis. Losing streak. In referance to the British actor Peter O'Toole who stard in such films as Murphys War, and was famous for not winning an acting Oscar after 8 nomminations.

"Dude!, we got friggen' O'Tooled on that pub crawl last night"

"Dude?!, Dave got totally O'Tooled by every girl on that pub crawl last night!...then again i was way too O'Tooled to keep track of them all"

O'Tooled by James March 6, 2004