I. ˈbə-mər noun
Etymology: probably modification of German Bummler loafer, from bummeln to dangle, loaf
Date: 1855
: one that bums
II. noun
Etymology: bum (II) + -er (II)
Date: 1966
1. : an unpleasant experience (as a bad reaction to a hallucinogenic drug)
2. : failure , flop