(electrical engineering, rail transport) A measure of the maximum output, usually expressed in horsepower, that can be obtained from the motors of an electric locomotive for a period of one hour without the motors overheating.

plural of hourly rating

Alternative form of semihourly.

plural of Zenithal Hourly Rate

(astronomy) The number of meteors a single observer would see in one hour under a clear, dark sky (i.e. up to the limiting apparent magnitude of 6.5).