howler vs bloomer

howler and bloomer both are nouns.

Word	Noun	Adjective	Verb	Adverb
howler	Yes	No	No	No
bloomer	Yes	No	No	No

As nouns, bloomer is a hypernym of howler; that is, bloomer is a word with a broader meaning than howler:

Other hypernyms of howler include blooper, blunder, boner, boo-boo, botch, bungle, flub, foul-up, fuckup, pratfall.

howler (noun)	bloomer (noun)
a glaring blunder	an embarrassing mistake
monkey of tropical South American forests having a loud howling cry	a flower that blooms in a particular way
a joke that seems extremely funny