To be forgotten; to slip into obscurity or to be no longer remembered. The passive form of 'wasureru' indicating something or someone is forgotten.
昔の流行歌は世代が変わると忘れられることが多い。
Old pop songs are often forgotten as generations change.
その事件は長い間忘れられていたが、最近話題になった。
That incident had been forgotten for a long time but recently came back into discussion.
誰も彼の名前を覚えておらず、彼は歴史の中に忘れられた。
No one remembered his name; he was forgotten in history.