to throw oneself into a task wholeheartedly or to come out in the open to act without disguise

为了赶在截止日期前完成项目，经理也赤膊上阵，亲自编写代码。

to go into battle bare-breasted or stripped to the waist

猛将许褚赤膊上阵，在大军面前与马超激烈交锋。