Answer:
In answer to the question 'What are miracles in atheism?' the answer is that there aren't any. A miracle is an extraordinary event attributed to divine intervention. In atheism there is no such thing as divine intervention- only human intervention- therefore no miracles. There is coincidence and in some cases luck but usually it is attributed to the work of real things- like humans. A 'miracle' is simply yet another way of de-glorifying humanity to try and prove the existence of god.
Also, "atheism" is not a discipline or system such as Islam, Catholicism or Judaism. To place your question in more accurate terms would be thus: What are the miracles in the absence of belief in a divine supernatural being that rules over human existence. That simply doesn't make sense. For a better understanding of atheism see the related question link provided below.