An "arc reactor" is a fictional device that generates clean and infinite energy, often found in superhero stories like Iron Man. It powers Iron Man's suits and other advanced technologies in the story. Full definition
We found out that his father was the one half to the ultimate arc reactor. (eclipsemagazine.com)
Remember when he built a miniaturized arc reactor in a cave out of spare parts? (inverse.com)
Vanko has a good enough reason to hate Tony Stark: Howard Stark and his father, Anton, worked on the original arc reactor designs together, but Howard had Anton deported. (businessinsider.com)