 An onigiri is a savory (salty) compressed ball of rice. It often has a filling or a coating of something savory, but there are also onigiri made of pre-flavored/mixed rice, as well as plain rice onigiri simply made with salt.  An onigiri is a savory (salty) compressed ball of rice. It often has a filling or a coating of something savory, but there are also onigiri made of pre-flavored/mixed rice, as well as plain rice onigiri simply made with salt. 