опростоволоситься {v.}
oprostovo`los'it's'ya
~ {literally} to appear with head uncovered.
To disgrace oneself, to be ashaimed. To find oneself in an embarrassing situation. To make a mistake or slip.
{origin}
In older times it was shameful to appear bare-headed in public or get one's hat teared off by smb.
"Джордж Буш опять опростоволосился, публично назвав Тайвань государством." — "George Bush has disgraced himself again by calling Taiwan a State."
See also:
оплошать
сплоховать