Since religion forms the basis of my morality, I am guided by that. To me, immorality is defined as something that religion says is a sin.
Violating the Ten Commandments, for example. Then there are the seven deadly sins (Pride, Envy, Wrath/Anger, Sloth, Avarice/Greed, Gluttony, and Lust).
An example of a moral absolute? Stealing would be immoral. Lying. Cheating. Not that I haven't done these things, mind you. But when I do, I feel bad about it. Some don't.
This is pretty basic stuff. Why do you ask?
Mainly because people on FR tend to denigrate moral relativism. I believe that all moral decisions are relative, in that most all things anyone can think of as being immoral, have been, at some time in history, condoned by the local majority. An absolute, to me, is something that no matter what, no one would do it. I believe the only absolutes in this world, are the physical ones.