Grand Magic

Grand Magic (大魔術(だいまじゅつ)) was a term used to refer to Angel Fall, a world distorting spell that occurs in Toaru Majutsu no Index, though it refers to other world distorting spells.

Background
The term grand magic was used to refer to Angel Fall alone, up until Tsuchimikado Motoharu's explanation to Kamijou Touma regarding the use of Feng shui by Kamijou Touya to arrange the souvenirs and charms in his home to create a magic array. Here, Motoharu states the danger of moving or touching the souvenirs as would create an entirely new magic array, therefore a new spell.

Motoharu lists examples, and all refer to them in as Grand Magic:
 * Great Magic (極大地震(アースシェイカー))
 * Abnormal Reverse World (異界反転(ファントムハウンド))
 * Eternal Cold (永久凍土(コキュートスレプリカ))

Trivia

 * The 2nd Toaru Majutsu no Index Soundtrack for the second season of the anime adaptation has the Dai Majutsu as the 7th track. Although none of the spells referred above are mentioned above, it most likely refers to the Large-scale spell La Regina del Mare Adriatico.