Meaning

noun an experience that is irritating or frustrating or disappointing

noun a bad reaction to a hallucinogenic drug

originEtymology tree English bum Proto-Indo-European *-yósder. Proto-Italic *-āzijos Latin -āriusnom. Latin -āriusbor. Proto-Germanic *-ārijaz Proto-West Germanic *-ārī Old English -ere Middle English -ere English -er English bummer From bum (“make unhappy”) + -er (agent noun suffix), originally US drug slang.

Etymology from Wiktionary, CC BY-SA 3.0