The phrase "blurring effect" refers to making something unclear or less sharp, like when you can't see something clearly because it appears fuzzy or out of focus. Full definition
These cameras will work together to deliver background blur effects for taking photos. (ibtimes.com)
Plus, because it films from a wider perspective, it creates a cool background blur effect that adds a different level to your video and photographs. (geekwrapped.com)
Hopefully it won't have the same blur effect in place that the first console release had. (gamespot.com)