A verbal exclamation used when a large (and often clumsy) mistake has been made, such as dropping a wine glass on the
floor, backing your car into a telephone pole, or forgetting a
girlfriend's
birthday.
Can also be used in an noun sense, as an affectionate name for a clumsy friend.
The phrase is intended as a suitable, non-vulgar replacement for the more commonly-used exclamations in this context (eg, "Son of a bitch!", "Fuck!", etc).