いだてんばしり [idaten bashiri] – a “Skanda dash”, refers to running with great speed. Skanda (idaten) is a Buddhist deity, who in folk lore was said to have chased down speedy demons and recovered sacred relics. Hence, he is known for his remarkable speed.
In fact, the word 御馳走 [gochisou] (yes, the one from the after-meal expression: gochisousama deshita) also comes from Skanda. The legend is that Skanda ran from place to place gathering food to prepare a feast for the Buddah.
Yamamoto flew out of the classroom like a bat out of hell.