A "radioactive spider" is a spider that has been exposed to harmful radiation. It is often used to describe a fictional spider in superhero stories, like Spider-Man, that gives someone special abilities or powers. Full definition
Not only is the theme song as infectious as radioactive spider bite, but it may even help teach my boys something about the nature of sin and temptation. (firstthings.com)
All I wanted to do is swing around like some kind of radioactive spider - style man. (stevivor.com)
Very good news for those of us who haven't been bit by radioactive spiders or gone through Treadstone training... (relevantmagazine.com)