An accidental or supposedly accidental failure of clothing to cover parts of the body intended to be covered.
Primarily used for referring to the exposure of breasts/areolae, but also acceptable for genitals, buttocks or underwear.
Her dress caught on the door knob and ripped. The resulting wardrobe malfunction was much to the delight of the guests. I bet she wished she had worn a bra and underwear under her dress.