Having two surfaces that both count. Double-sided tape is sticky on both faces, so you can stick two things together and not see the tape. Double-sided paper, a double-sided leaflet, or double-sided printing has words or pictures on both faces, not only the front. You will hear it in offices, schools, and craft shops — practical, everyday English. It is about objects. A person who is false on the outside is two-faced, not double-sided; nobody serious calls a person double-sided.