'Grand Festival'. The top class of festivals as contrasted with chusai (middling festivals) and shosai (minor festivals). It refers to major festivals such as those that attract a kenpeishi. After the Meiji restoration these festivals were fixed by law, but in the postwar period they are determined by the Jinja Honcho in the "jinja saishi kitei" (regulations on shrine festivals). According to these regulations the taisai may for example be a rei-sai or reitaisai ([great] regular festival), niiname-sai (harvest festival), chinza-sai (enshrinement ceremony), senza-sai (shrine-transfer rite) goshi-sai or a festival which has a special historical connection with the shrine.
A Popular Dictionary of Shinto. Brian Bocking.