提示：点击例句中的单词，就可以看到词义解释

So I rolled up my sleeves , knuckled down .

于是我挽起袖子，开始认真地投入工作中。

He knuckled me in the chest .

他用指关节敲击我的胸部。

His knuckled were white as he gripped the steering wheel .

他屈服，因为他是白人抓住方向盘。

It 's high time you knuckled down to some hard study .

你该开始刻苦学习了。