The indices status API allows to get a comprehensive status information of one or more indices.
$ curl -XGET 'http://localhost:9200/twitter/_status'
The status API can be applied to more than one index with a single call, or even on _all the indices.
$ curl -XGET 'http://localhost:9200/kimchy,elasticsearch/_status'
$ curl -XGET 'http://localhost:9200/_status'