Taisha is a term used to refer to a rank of Shinto shrines.
A (the characters are also read à Âyashiro) is literally a "great shrine" that was classified as such under the old system of shrine ranking, the , abolished in 1946.
Originally Taisha referred to the 203 Myojin Taisha or the 492 Shikinai Taisha listed in the Engishiki Jinmyocho
The term became more strict in the Empire of Japan. In that time it almost always referred to Izumo-taisha. After the war, many shrines with the rank of taisha, such as the former Kanpei Taisha and the former Kokuhei Taisha Shrine, started calling themselves taisha.
Izumo Taisha wants to be the only shrine to use the name.
There are some shrines which used to call themselves Taisha but later changed their names