Master hash
From Mini-blockchain Project
A typical hash tree structure will have a root/master hash which is derived from all the other hashes in the tree. The master hash represents the digest/fingerprint of the entire hash tree and is used to detect any changes to any part of the data in the tree and thus achieve consensus on its state.
Within the mini-blockchain scheme, the term master hash refers to the hash which encapsulates all other hashes within the account tree. Miners apply all the transactions in their blocks to the account tree and include the resulting master hash in the block header so that others can verify it.