The phrase "slop over" refers to the overflow of liquid or substance from a container. There are a number of synonyms that could be used in place of this term, depending on the context in which it is used and the degree of overflow involved. Some possible alternatives might include spill, leak, ooze, pour out, run over, or flow out. These terms might be used to describe situations where a drink spills out of a cup, a pot boils over on the stove, or a container leaks during transportation. By using different synonyms for "slop over," writers and speakers can effectively convey the meaning and intensity of the situation they are describing.