"轻蔑一笑"可以用英文表达为"sneer contemptuously"或者"sneer in contempt".
"Sneer"是一个动词，意思是带着轻蔑或嘲笑的神情嘲笑。
"Contemptuously"是一个副词，意思是带着轻蔑或鄙视的心态。
来源：
这个短语源自于英语单词"sneer"和"contemptuously"。"Sneer"来自于中世纪英语"snerian"，意思是嘲笑或讥笑。"Contemptuously"来自于拉丁语"contemptus"，意思是轻蔑或鄙视。
例句：
He sneered contemptuously at the suggestion. 他对这个建议轻蔑一笑。
She sneered in contempt at his weak attempts to defend himself. 她对他弱小的辩解轻蔑一笑。