When something "smells high heaven", it typically means that it has a very strong and unpleasant odor. There are many synonyms to describe such a smell, including foul, putrid, malodorous, rank, rancid, noxious, pungent, and fetid. Each of these words conveys the idea of a smell that is offensive and difficult to bear. Other words that could be used include acrid, sour, musty, moldy, and dank. Describing an unpleasant odor can be difficult, but using synonyms like these can help to capture the intensity and unpleasantness of such a smell.