Twintip

Twintip is a design principle and, in a figurative sense, a ski with a heel bent similar to the tip, with different heights. In contrast to the gradual rise of the rocker, it has a bend comparable to the tip. It occurs in cross-country skis and especially in freestyle skis, there may be a hint of twintip in others as well. Twintip increases the versatility of the ski (riding on a switch, freestyle landings), the feet can better traverse the terrain and bumps. On the contrary, they reduce the dynamics at the end of the arc (see rebound) and the autokinetic effect of the heel.

Source: https://snow.cz/clanek/1546-co-je-to-lyze-aneb-slovnicek-pojmu