When something is said to "go over big", it means that it is received very well or enthusiastically. Antonyms for this expression could vary depending on the context in which it is being used. Some opposite words that could be used include "fails miserably", "falls flat", "disappoints", "flops", "bombs", or "underwhelms." These words indicate that the thing being described did not achieve the desired success or response. Alternatively, less extreme terms like "moderately successful," "receives average interest," or "just okay" can also be used as antonyms for "goes over big".