bumper sticker

noun2

1. •
   An adhesive label or decal, usually applied to the bumper or back end of an automobile, and displaying a short political, promotional, philosophical, or humorous message.

   • He has a bumper sticker on his van that reads "faster than a speeding ticket".
2. •
   (figurative) Canned insight; a slogan or saying that is trite or superficial.

   • "It's like a status thing, you know? 'My kid's special because he's got a peanut allergy.' I'm surprised they don't have a bumper sticker for it." — 2008