noun
99th birthday
A celebratory term for a person's 99th birthday, derived from the kanji 白 (white) being seen as 百 (100) minus the top stroke 一 (1). Used in contexts like 白寿のお祝い (celebration of one's 99th birthday).
祖母は来月、白寿を迎えます。
My grandmother will celebrate her 99th birthday next month.