Blunderer

a gross, stupid, or careless mistake:
That’s your second blunder this morning.
to move or act blindly, stupidly, or without direction or steady guidance:
Without my glasses I blundered into the wrong room.
to make a gross or stupid mistake, especially through carelessness or mental confusion:
Just pray that he doesn’t blunder again and get the names wrong.
to bungle; botch:
Several of the accounts were blundered by that new assistant.
to utter thoughtlessly; blurt out:
He blundered his surprise at their winning the award.
Historical Examples

Barlasch of the Guard H. S. Merriman
Bardelys the Magnificent Rafael Sabatini
Kincaid’s Battery George W. Cable
Ten Years Later Alexandre Dumas, Pere
The Printer Boy. William M. Thayer
The Shadow of Life Anne Douglas Sedgwick
The Virginian Owen Wister
Crestlands Mary Addams Bayne
The Fifteen Decisive Battles of The World From Marathon to Waterloo Edward Creasy
German Problems and Personalities Charles Sarolea

noun
a stupid or clumsy mistake
a foolish tactless remark
verb (mainly intransitive)
to make stupid or clumsy mistakes
to make foolish tactless remarks
often foll by about, into, etc. to act clumsily; stumble: he blundered into a situation he knew nothing about
(transitive) to mismanage; botch
v.
n.