blunder

BLUNDER noun

[ C ] uk/ˈblʌndər/ us
a serious and often stupid mistake

промах
a series of financial blunder s
blunder verb uk/ˈblʌndər/ us
[ I ] to make a serious mistake

допускать промах
  blunder around/into, etc
to move somewhere in a heavy way, as if you cannot see well

двигаться ощупью
He blunder ed around, looking for the light switch.