Definitions by rmb

0day 

Used in IRC or other chat (in the negative) as a sarcastic comment to something already said or "old news."

<person_1> X just happened, check out website
<other people> Very interesting, person_1!

... 3 hours later ...

<person_2> OH EM GEE X JUST HAPPENED website
<other people/person_1> That's so not 0day.

0day by rmb September 4, 2006