hopeium

colloquial derogatory uncountable

(colloquial, derogatory) A clinging to unreasonable or unfounded hopes.

Japanese Meaning

（軽蔑的な用法で）根拠のない、非合理な希望にすがる状態 / （侮蔑的に）現実的な根拠のない楽観視、妄信的な期待

Even after the third defeat, his insistence that the team would still get promoted felt like pure hopeium.

3回目の敗北の後でも、チームがまだ昇格すると彼が主張するのはまさに根拠のない希望に過ぎなかった。

Sense（1）

(colloquial, derogatory) A clinging to unreasonable or unfounded hopes.