Snowflake
A snowflake was a single crystal made of frozen water that fell as snow.
In 2364, Geordi La Forge compared the Crystalline Entity to a giant snowflake crystal, only more complex.(TNG: "Datalore")
Three years later, Noonien Soong referred to it in the same manner, saying he never thought he'd have to escape from a giant snowflake. (TNG: "Brothers")