"Draw the line" is an idiomatic expression that means to set a limit or boundary on what is acceptable or tolerable. There are several synonyms for this phrase that can be used to convey a similar meaning, including "establish boundaries," "set limits," "define the parameters," "set the bar," "delineate," and "define the border." These phrases all imply the need to establish clear boundaries in order to maintain order and respect. The ability to draw the line is an important skill that can help individuals navigate challenging situations and communicate their expectations clearly to others.