Hum, the sound one makes when thinking.

Human resource management, the academic theory and business practice of managing a workforce

Halifax Regional Municipality, the capital city of the province of Nova Scotia, Canada

Heart rate monitor, a device that allows a user to measure his or her heart rate in real time

His or Her Royal Majesty, a style used by King-Emperors and their consorts as heads of imperial dynasties that were simultaneously royal, see Imperial and Royal Majesty

Human Race Machine, a computerized console created by Nancy Burson