When you're out bar-hopping until the wee hours of the morn moving from a bar that's closing to a later-closing-bar until it's just time to call it a night and bang somebody. Event usually occurs from about 2AM to 4AM.
Adjective. The term is used to indicate that someone or something has a nerd or geek-like quality. It is also used by geeks to describe other, more hard-core geeks. It's connotation may be positive or negative depending on tone.
The term comes from the software industry, where kernel programming is among the most technically involved. From an informal standpoint, the more connected people are with kernel software, the higher the chances are of them being geek-like.
John is alwaystalking about role-playing games on his computer - he's close to the kernel.