H

Hashcash

A proof-of-work mechanism, invented by Blockstream CEO Dr. Adam Back, intended to stop spam and anonymous remailers that is now used as the basis of Bitcoin's mining algorithm.

Hashrate

An aggregate measure of how many hashes Bitcoin miners produce per second in the Proof-of-Work consensus algorithm.

HODLer

An intentional misnomer for 'holder'; a person who keeps long-term savings in Bitcoin.