Deutsch: Schlüsselloch / Español: Ojo de cerradura / Português: Buraco da fechadura / Français: Trou de serrure / Italiano: Buchi della serratura /
Keyhole refers to an opening in a garment usually around the Cleavage area or upper back so named because it is supposed to resemble the shape of keyhole opening, although it is more of a teardrop shape in reality. Keyhole openings are usually used in conjunction with a high neck or Mandarine Collar.Found on dresses, shirts and swimwear, a Keyhole is a teardrop-shaped opening or an oval-shape cut out usually on the neckline or below a jewel neckline.
Other /More definition:
Keyhole refers to an oval-shaped opening often in the neckline or top of the back, bodice or back of a dress, gown, jumpsuit, or catsuit, etc.
Example is a white gown with keyholes worn by actress Diane Lane at the 76th annual Academy Awards (Oscar) in Hollywood.