be down in the dumps

To be visibly sad or depressed. Molly's been moping around all week, and I have no idea why she's so down in the dumps. Rob has been down in the dumps ever since Gloria broke up with him. He's been down in the dumps ever since he found out he didn't get the job.

down in the dumps, to be

To be sad or dispirited. The “dumps” referred to are not the modern rubbish heap but a heavy, oppressive mental haze or dullness (from the Dutch words domp and German dumpf). The expression was used several times by Shakespeare (Titus Andronicus 1.1; The Taming of the Shrew 2.1; Much Ado about Nothing 2.3) and was well known as “in the dumps” until the eighteenth century. See also down in the mouth.