Dos-a-dos, from the Spanish, literally "back-to-back", is applied to:

• Books bound in pairs back-to-back, such as Ace doubles.
• Dosado, also spelled Dos-a-dos, a dance move where partners pass back-to-back and return to a facing postition.
• A seat where two or more sit back-to-back, a furniture, or in a carriage (typically a dogcart), or other conveyance.
• Dos-a-dos (carriage), a carriage with the dos-a-dos seat.