plural of hour circle

(astronomy) The great circle through an object whose location is to be determined and the two celestial poles.

plural of hour-glass

plural of hour glass

(historical, obsolete) A unit of computing power equal to 1000 girl-hours.

(historical, obsolete) A unit of computing power in the context of 1940s–1970s technology equal to one female worker working for one hour, for example, writing code or entering data to punch cards.

Thirty minutes.

(idiomatic) the time when help is most needed

An hour of operation of an engine.

A very early or late time of day.