An O Party is a group of people who have had sex with really large objects until they have stretched the anus/twat into a huge O shape. They then gather around in a circle, still exposing their stretched holes, around a group of men. The men then ejaculate into each stretched hole. Other things may be used to pour into stretched holes, like syrup or oil.
It caught me by suprise that the party I attended to last week was actually an O party!
by Wasabimoto December 14, 2007
n. That time of night when teenagers and young adults can be expected to arrive at a party.

The expression is used mostly among college-aged adults who typically party-hop or bar-hop on the weekends. The ambiguity of the phrase avoids the potentially embarrassing situation of a guest arriving too early for a party or a host(ess) waiting for guests to arrive. See also party foul.

The term is most often encountered on Internet invitations or mass e-mails advertising a private party.

The time is generally understood to be between 10pm and midnight.
"What time are you heading over to D's house?"

"Party o' clock"
by mxm February 9, 2009