An imagined event or sequence of mental images, such as a daydream, usually fulfilling a wish or psychological need.
Fiction characterized by highly fanciful or supernatural elements.
I'm going with escape on this one. Fantasy is sort of like the "cuddle blanket" of the mind. Like a toddler, we'll find it, invent our intensions concerning it, and eventually carry it around with us.
And then, sometimes, we'll find others with similar blankies, then to sit down and have a brainstorming tea party of sorts...
Not to say it's a bad thing, it should just be used like every great thing and not to a great extent. Or, better put, matter over mind.
~Ka