Acid test is a term that refers to a severe or demanding examination of something's quality or worthiness. There are various synonyms for acid test such as decisive moment, litmus test, crucial test, make-or-break time, moment of truth, acid test, breaking point, tipping point, point of no return, and defining moment. Each of these synonyms can be used interchangeably in context with acid test to convey the same meaning. However, each may have slightly different connotations depending on the situation. For instance, a tipping point may suggest reaching a turning point after a period of buildup, while a defining moment describes one specific event that determines a direction or result.