The definition of a bummer is slang for something undesirable, unpleasant or annoying, or is slang for a bad reaction to a drug, or is a lazy person who hangs around all day without a job or purpose.(noun)
See bummer in Webster's New World College Dictionary
Origin: < bum + -er
See bummer in American Heritage Dictionary 4
Origin: From bum1, adj.
Origin: . Sense 3, probably from German Bummler, loafer
Origin: , from bummeln, to loaf.
Learn more about bummer