A breakfast cereal made from grains of rice which are steamed, sweetened, and then heated rapidly in the manner of popcorn; (also in singular) a piece of this cereal.
Origin
1920s; earliest use found in Pittsburgh Courier.
Definition of rice crispies in US English:
rice crispies
noun
A breakfast cereal made from grains of rice which are steamed, sweetened, and then heated rapidly in the manner of popcorn; (also in singular) a piece of this cereal.