noun
waste of money; money down the drain
Colloquial expression likening wasted money to something thrown into a gutter. Often used in phrases like 金ドブに捨てる (throw money down the drain).
See also: ドブに捨てる
そんなガラクタを買うなんて金ドブだよ。
Buying junk like that is a waste of money.
高い会費を払ったけど、全然使わなくて金ドブだった。
I paid a high membership fee but never used it—total money down the drain.
Compound of 金 (money) and ドブ (ditch/gutter), literally 'money ditch'. The expression likely derives from the phrase ドブに捨てる (throw into a ditch), implying money is wasted as if discarded into a gutter.