Up-and-down describes something that keeps changing between good and bad, high and low, or success and failure. A basketball player having an up-and-down season might score 30 points one game and only 5 the next. A friendship going through an up-and-down period has great days mixed with arguments and hurt feelings.

The phrase captures that roller coaster feeling of inconsistency. When your grades are up-and-down, you might ace a math test on Monday but do poorly on a spelling quiz on Friday. A business with up-and-down profits makes lots of money some months and barely breaks even in others.

Up-and-down can also describe a literal vertical motion, like the up-and-down movement of a yo-yo or an elevator. But most often, people use it to talk about performance, mood, or fortune that won't settle into a steady pattern.

The opposite would be steady or consistent. Athletes work hard to avoid up-and-down performance because coaches and teammates need to know what to expect. The same goes for students: steady effort usually beats unpredictable bursts of brilliance followed by stretches of low effort.