Literally, the Four Directions (Japanese).
In Aikido, shiho nage is the four-directions throw. It is based on a circular sword cut which concludes behind the attacker. In body techniques, this usually means the attacker, nage, takes a backfall or breakfall.
In Classical Aikido, there are several other ideas attached to the idea of shiho. Shiho giri is a solo form performed with sword or bokken. It is a part of the exercises which one should perform at the beginning of class, and is used to calm, center, and purify (see misogi) the self.
Additionally, shiho is the first of the basic Pillars of Classical aikido. Applied to every-day life, shiho means gratitude. For further information, see the Four Gratitudes.