Digital Rights Management or, more correctly, Digital Restrictions Management.
Any of the group of technologies intended to supress piracy by imposing use restrictions on all copies of a given product. The reason why most of people download their songs off eMule instead of buying the CDs. One of the most braindead ideas in the history of computing. Encourages piracy by making the pirated product more valuable than the legal one. While DRM significantly hurts the average user by restricting his/her use of the product, it is only a minor nuisance to those it is intended against (crackers, pirates etc.). Object of religious veneration among the entertainment industry despite its complete ineffectiveness.
Enhanced DRM enforcement is the core feature of Windows Vista, which makes it ca. 30% slower than XP.
This new CD of mine is DRM'd and I can't put the tracks in my MP3 player