"Grow worse" is a phrase used to describe a situation that deteriorates over time. However, there are many other words and phrases that can be used to convey this meaning, including worsen, deteriorate, decline, degrade, deteriorate, degenerate, sink, plummet, dwindle, degrade, worsen, deteriorate, slide, slip, worsen, deteriorate, decline, ebb, descend, regress, backslide, decay and retrogress. Each of these words and phrases carries slightly different connotations and can be used in different contexts depending on the severity and speed of the decline. Whether describing personal or global situations, having a range of synonyms available can help to convey the nuance of any given situation.