汉语中的“查字典”，说成英语通常是 look up sth in a dictionary 或 consult [refer to] a dictionary。如：

I refer to the dictionary frequently. 我经常查阅词典。

You can look the word up in the dictionary. 你可以在词典里查这个词。

He often consulted a dictionary when he read the book. 他读这本书时经常查字典。

I looked the word up in the dictionary to refresh my memory of its exact meaning.  我查了词典，以便弄清这个词的准确意思。

I often look up the words I don’t know in the dictionary or on the Internet. 我经常在字典里或网上查找我不认识的单词。

“Is that the correct spelling?” “I don’t know―look it up in a dictionary.”  “那是正确的拼写吗？”“我不知道――查查词典吧。”

I didn’t know what “loquacious” meant and had to look it up in a dictionary.  我不知道loquacious这个是什么意思，所以只好查了词典。

有不少人认为英语习惯上不能直接说 look up the dictionary, 其实这种表达在英语中也可以用，只是比较少见而已。例如：

I spend more time looking up the dictionary than reading the book. 我读这本书时查字典的时间还多些。――摘自 L. G. Alexander 编《新概念英语》（外研社）

Look up the dictionary and explain the meaning of the italicized words. 查字典然后解释斜体词的意思。――摘自张汉熙编《高级英语》（商务印书馆）