Blunder

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.
Contemporary Examples

Newt Gingrich’s Fear Factor: What If He Loses the Florida Primary? Howard Kurtz January 30, 2012
World Cup Wrap-Up Joshua Robinson June 11, 2010
The Worst Governor for Women Linda Hirshman March 3, 2010
Why Bin Laden Was Not Taken Alive Paul Campos May 5, 2011
Hey Daniel Tosh—No One Believes Your Lame Twitter Apology Jesse Singal July 13, 2012

Historical Examples

The Life of John Marshall (Volume 2 of 4) Albert J. Beveridge
The Roof of France Matilda Betham-Edwards
Liverpool a few years since James Aspinall
The International Monthly, Volume 3, No. 2, May, 1851 Various
Eyes Like the Sea Mr Jkai

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.