Is their such a configuration as multiple indexers in an enterprise environment but not consider it a cluster?

I have an environment with three search heads, three indexers, one license server (also acts as the deployer), and one deployment server (distributing forwarder configurations, inputs.conf). This environment is setup with a replication factor of 2. Would you say the above configuration is distributed as well as clustered? Also, does cluster alway refer to the indexer group or is it right to say "we have a search head cluster" as well as " we have an index cluster"? Thanks Gary