The idea that a person will be close to a significant other until something tears them apart. After what is usually a few years the two people will meet up again and be attracted to one another. Such as a boomerang leaves but comes back.
Friend 1: "John started seeing Claudia again; its been 4 years since they were together."
Friend 2: "I told you the Boomerang theory was real!"
Friend 2: "I told you the Boomerang theory was real!"
by Toichiro October 14, 2014