I am new to user experience as well and I refer you to http://de.slideshare.net/Luristic/the-anatomy-of-rich-user-experience
it is a white paper on rich user experience that also presents quite a few definitions!
Below are few good definitions of user experience: User Experience (UX
or UE) is a term used to describe the overall experience and
satisfaction a user has when using a product or system. It most
commonly refers to a combination of software and business topics, such
as selling over the web, but it applies to any result of interaction
design. Wikipedia
User Experience (UX or UE) encompasses all aspects of the end-user's
interaction with the company, its services, and its products. The
first requirement for an exemplary user experience is to meet the
exact needs of the customer, without fuss or bother. Next comes
simplicity and elegance that produce products that are a joy to own, a
joy to use. True user experience goes far beyond giving customers what
they say they want, or providing checklist features. In order to
achieve high-quality user experience in a company's offerings there
must be a seamless merging of the services of multiple disciplines,
including engineering, marketing, graphical and industrial design, and
interface design. Nielsen Norman Group
User Experience (UX or UE) encompasses all aspects of a digital
product that users experience directly—and perceive, learn, and
use—including its form, behavior, and content. Learnability,
usability, usefulness, and aesthetic appeal are key factors in users’
experience of a product. Pabini Gabriel-Petit
User Experience (UX or UE) encompasses the visual appearance,
interactive behavior, and assistive capabilities of software. From an
application's graphical user interface to its use of additional
technologies such as speech recognition and speech synthesis, a
cohesive and professional user experience is what Mac users have come
to expect. Apple Leopard Reference Library
You might furthermore find information on User Experience as a
honeycomb as defined by Peter Morville which is an extension of Jesse James
Garrett’s UX diagram.