Tarmac was a tar-based construction material that was pliable and gooey when hot, but extremely hard when cooled. It was often used in the construction of roads.
The Tenth Doctor and Martha Jones, once used a spot of freshly-laid tarmac to capture a sabre-toothed tiger that had escaped from the Museum of the Last Ones. After luring it into the hot tarmac, the Doctor used his sonic screwdriver to rapidly cool the tarmac and freeze the tiger's paws. (PROSE: The Last Dodo)
When the Fifteenth Doctor was forced to leave Ruby Sunday on her for a bit when they attended a ball in Bath, England in 1813, he told her to just try to not get engaged or accidentally invent tarmac, stating that 1902 had gotten away from him. (TV: Rogue [+]Kate Herron and Briony Redman, Doctor Who series 14 (BBC One and Disney+, 2024).)