The word "over estimate" can be used to describe the act of overvaluing something or someone, estimating their worth or capabilities to be higher than they actually are. However, there are many antonyms for this phrase, which describe the opposite action. Some of these words include "underestimate," "undervalue," "underappreciate," "downplay," and "disparage." To underestimate something means to value it lower than it should be or to underestimate someone's abilities. To undervalue means to not recognize the true worth of something or someone, and to underappreciate someone means to not fully recognize their contributions. To downplay means to reduce the importance or value of something, and to disparage is to speak negatively about someone or something, reducing their worth in the eyes of others.