In regards to the anime Bleach
], a shikai is the first release of a zanpakuto, the sword used by shinigami
]. Each shikai has a special ability.
To release the shikai form of a zanpakuto, one must call it's name (eg; "Scatter, Senbonzakura", "Awaken, Benihime", "Dance, Sode no Shirayuki"). This is no longer necessary when one has attained bankai, the second release.