adjective describing a person. The person metaphorically "shoots down" anything you may say to that person. It can be an idea or a plan, but it is usually shot down.
Person 1: "Hey, it's beautiful outside, let's go for a walk."
Person 2: "No." <---- Person 2 is a shooter downer.
Person 2: "No." <---- Person 2 is a shooter downer.
by Weird Beard March 22, 2013