>By "high-temperature" superconductivity, physicists mean liquid nitrogen temperature

...sure, but there are superconductors at a lot warmer temperatures than 77K.

mercury barium calcium copper oxide at 133 K (atmospheric pressure). http://adsabs.harvard.edu/abs/1993Natur.363...56S

Hydrogen Sulfide at 203K, under pressure:

http://physicsworld.com/cws/article/news/2015/aug/21/hydroge...