To repay for something that was given to you.
To be nice and give back to someone who gave you something.
"Now without making any sudden movements, give them an energon goodie" -Kup
"This is getting expensive!" -Hot Rod
"Don't worry, they'll reciprocate." -Kup
"I thought they were supposed to reciprocate! No more!" -Hot rod
(Taken from the Transformers movie)