动词过去式:unbuttoned 过去分词:unbuttoned 现在分词:unbuttoning 第三人称单数:unbuttons
un-=the reversal of an action 置于动词前，表示这个动词的相反的动作
v [Tn] undo the buttons of (a jacket, etc) 解开（上衣等）的钮扣.
to undo the buttons on a piece of clothing
He took off his sweater and unbuttoned his shirt.