Ascending to a whole other level of skill in something related to the electronics underground, such as being proficient at video gaming, hacking, phreaking, etc.
"Dude, did you see how manyfucking combo moves I just executed? That was 1337!"
the year that all "teh ub3r 1337 hAx0rs" were born in and even since then they have been little faggots who sit at their computer 1337 hours a day watching meatspin and call it hax0ring
It means "elite" as in "elite speak" (sometimes called hacker) which is this odd language net people speak where they replace letters with numbers, impossible to read.