居然 means "surprisingly" or "unexpectedly" in Chinese. It is composed of two characters, 居 (jū) meaning "to live" or "to reside," and 然 (rán) meaning "then" or "in that case." The word can be used to express surprise or amazement at something that has happened.

Here are some example sentences in Chinese and English:

你居然去了北京？ (Nǐ jūrán qù le Běijīng?) "You went to Beijing unexpectedly?"

他居然会跳舞！ (Tā jūrán huì tiàowǔ!) "He can dance surprisingly!"

居然有人敢挑战我？ (Jūrán yǒurén gǎn tiǎozhàn wǒ?) "Is there really someone who dares to challenge me?"

In these examples, the speaker uses 居然 to express surprise or amazement at something that has happened or something that someone has done.