I have found a definition:
http://www.umts-forum.org/what_is_umts.html
What is UMTS?
UMTS stands for 'Universal Mobile Telecommunications System'
UMTS is one of the major new 'third generation' (3G) mobile communications systems being developed within the framework defined by the ITU and known as IMT-2000
UMTS will play a key role in creating the mass market for high-quality wireless multimedia communications that will exceed 2 billion users worldwide by the year 2010. This market will be worth over 1 trillion US dollars to mobile operators over the next ten years
UMTS will enable the wireless Information Society, delivering high-value broadband information, commerce and entertainment services to mobile users via fixed, wireless and satellite networks
UMTS will speed convergence between telecommunications, IT, media and content industries to deliver new services and create fresh revenue-generating opportunities
UMTS will deliver low-cost, high-capacity mobile communications offering data rates as high as 2Mbit/sec under stationary conditions with global roaming and other advanced capabilities