This was taken from a literary agent's blog (http://literaryagentny.com/). This defines their idea of high concept in regards to story and books. Works for movies, too.
What is High-Concept?
•High-concept is a welcome slap-in-the-face for publishing professionals
who’ve been lulled to sleep by thousands of boring submissions (hey, it’s the truth).
•High-concept instantly communicates an idea and gives it context.
•High-concept is the difference between good and great.
•High-concept is taking something timeless and making it timely.
•High-concept is making something familiar and/or faded… fresh.
•High-concept is clever (but that doesn’t mean it isn’t also authentic).
•High-concept is standing out, getting everyone’s attention, creating curiosity.
•High-concept sometimes (but not always) means being bold, creating a spectacle,
and/or creating controversy.
•High-concept is memorable.
•High-concept is often newsworthy and media-friendly.
•High-concept gets people talking, sometimes shouting, other times whispering.
•High-concept is simply positioning or repositioning.
•High-concept is what Houdini created when he unchained himself from manacles
and escaped while hanging upside down 30 stories above the ground (but it’s not magic).
•High-concept is what P.T. Barnum used to fill his tents, employing the talents of
Tom Thumb (but you don’t have to be a clown or create a circus to do it).
•High-concept is embracing your role as both expert and entertainer or master of intrigue
and mystery (even if you’re just writing cookbooks).
•High-concept might mean using a metaphor to make the mundane seem magnificent.
•High-concept often bends (and sometimes breaks) rules and conventions.
•High-concept is arguably more important than the characters in a novel because
no one will ever meet (or care about) your characters without it.
•High-concept might capitalize on current trends (and sometimes creates new ones).
•High-concept understands that important themes, valuable content, and
a beautiful writing style aren’t always enough.