Hashing is a specific case of indexing:
Indexing is a general name for a process of partitioning intended at speeding up data look-ups. Indexing can partition the data set based on a value of a field or a combination of fields. It can also partition the data set based on a value of a function, called hash function, computed from the data in a field or a combination of fields. In this specific case, indexing is called data hashing.