'bummer' definitions:

Definition of 'bummer'

From: WordNet
noun
An experience that is irritating or frustrating or disappointing; "having to stand in line so long was a real bummer"
noun
A bad reaction to a hallucinogenic drug

Definition of 'bummer'

From: GCIDE
  • bummer \bum"mer\ (b[u^]m"[~e]r), n.
  • 1. An idle, worthless fellow, who is without any visible means of support; a loafer; a dissipated sponger; one who bums. [Slang, U.S.] [1913 Webster]
  • 2. an unpleasant event, experience, or situation; as, getting caught in a cloudburst while wearing my best suit was a bummer. [Slang, U.S.] [PJC]

Synonyms of 'bummer'

From: Moby Thesaurus