Quick Definition: An experiment should be able to be repeated and achieve the same result, else there is an error
From Rational Wiki:
Having the experiment repeated by an independent investigator ‘reduces’ the impact of a single study’s experimental error and increases the chances of the hypothesis being accepted by the scientific community. Of course, reproducibility, alone, is not enough when even random numbers can reproduce prior results.
One of the signs of pseudoscience is a lack of reproducibility in their experiments.