ㅠㅠ /yu-yu/
Crying / Sad face
Represents tears streaming down. The ㅠ character looks like tears falling. More ㅠ's = more sadness. Also written as ㅜㅜ (smaller tears).
Examples
시험 망했어 ㅠㅠ
I failed the exam (crying)
보고 싶어 ㅠㅠㅠㅠ
I miss you so much (sobbing)