Intuition is the immediate awareness of truth without the benefit of logic or mental reasoning. In a religious sense, it is the power of insight without conscious reasoning, typically attributed to a momentary divine or angelic gift.
Philosophically, it is an immensely problematic concept as it requires a special mental faculty of intuition, with no readily describable mechanism of causation for the knowledge thus aquired. Most attempts to preserve the objective truth of moral statements fall back on a form of intuitionism: the statement "Kindness is better than cruelty," for example, has massive intuitive appeal, even though the concepts within it defy meaningful empirical analysis.
As Bertrand Russell put it: "I cannot see how to refute the arguments for the subjectivity of ethical values, but I find myself incapable of believing that all that is wrong with wanton cruelty is that I don't like it." 
- Philosophy, 1960, "Notes on Philosophy" http://uk.encarta.msn.com/quote_1861989747/Ethics_I_cannot_see_how_to_refute_the_arguments_for_the.html