1) warez obtained on the day of, or slightly before, its official (legal) release.
2) Information that is not publicly available until it is rapidly disseminated in the online community. Often contains the details of new computer vulnerabilities, allowing exploiters to comprimise computer networks before system administrators have a chance to secure their networks.

When a reply to a tweet gets more likes than the tweet it was replying to, usually indicating the unpopularity or stupidity of the original tweet

Used by software pirates to describe material (software, music, movies) released the same day it hits stores

Relating to a security vulnerability or exploit that has not been released or known about by the general public. Often begged for on lists such as "Full-Disclosure" by kiddies.
Sometimes lamers will call it Ohday (OH-day)

Generally used when talking about cracked software, cracked and released the same day as the software was legally available.

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