To underplay something is to talk about it, or act about it, as if it were smaller, calmer, or less serious than it really is. The thing is real; you just make it sound like less. A doctor who says "there's a small problem with your heart" when the problem is not small is underplaying it. A company that says a data leak "affected some accounts" when it affected millions is underplaying it. Notice that the word carries a soft judgement: when I say you underplayed something, I usually mean you should have said more. It is the natural opposite of exaggerate. There is a second use, from acting: an actor underplays a part when they act it in a quiet, held-back way instead of a big dramatic way — and here the word is often praise, because a quiet performance can hit harder. English also has the phrase 'underplay your hand', from card games: you have strong cards but you bet small, so you win less than you could have. People use that about job interviews and negotiations. The word is fairly formal — you meet it in news writing and reviews more than in daily chat. In daily chat people say 'play down', which means the same thing: "He played down the injury." Small warning: underplay is not a word about doing too little work or playing sport too little. It is about how you present something.

淡化、輕描淡寫（把事情說得比實際小）；演戲時指「收著演」。注意不是「玩得太少」。