“Try not to leave a mess when you die,” intones Poison Ivy (Uma Thurman) in this loud, uninspired, and interminable third sequel; but the movie doesn’t take her advice. There’s a lot of designer leather and designer heavy metal and one designer disco set after another, plenty of tacky camp references to Marlene Dietrich and Mae West, plus Star Wars beasties, AIDS metaphors, computer details, stupid “cold” puns from Arnold Schwarzenegger (playing villain Mr. Freeze), and dollops of insincere sentimentality involving the heroes’ butler (Michael Gough). But it’s clear that writer Akiva Goldsman and director Joel Schumacher are bereft of ideas and using the MTV clutter as a cover-up. A few nice moments are offered by spunky Alicia Silverstone, but the standard for humor and ingenuity is set by Robin (Chris O’Donnell) calling Batman (George Clooney this time around) a “dick.” With Pat Hingle and Elle Macpherson.