to attempt to master a difficult videogame/puzzle/craft to perfection in a matter of days by sitting on your ass for hours on end as if (or because) you have no life.
To do months of work within days, reject social invitations, and only leave the house to buy take-away because you must work hard to do well. Synonymous with IT certifications or playing computer games.
Sorry dude, I cant come out tonight. I've gotta no-life Cisco, as I've only got 5 days left to complete the last 6 exams of my certification.
Yea man, the only way your going to finish that work is by No-Lifing it.