1a period of time equal to a twenty-fourth part of a day and night and divided into 60 minutes:an extra hour of daylightrates have ranged from $9 to $32 an hour [as modifier, usually with preceding numeral]:a two-hour operation
a less definite period of time:during the early hours of the morning
the distance traveled in one hour:Ocean City is less than an hour away
2a point in time:I wondered if my last hour had come
a time of day specified as an exact number of hours from midnight or midday:the clock in the sitting room struck the hour
(hours) [with preceding numeral] a time so specified on the 24-hour clock:the first bomb fell at 0051 hours
the time as formerly reckoned from sunrise:it was about the ninth hour
3a fixed period of time for an activity, such as work, use of a building, etc.:shortened working hoursthe dinner hour
4 (usually hours) (in the Western Church) a short service of psalms and prayers to be said at a particular time of day, especially in religious communities.
5 Astronomy 15° of longitude or right ascension (one twenty-fourth part of a circle).
any time, especially outside the time considered usual for something:intruders had access at all hoursteenagers expect to be allowed to stay out to all hours
keep late hours
get up and go to bed late.
keep regular hours
do the same thing at the same time every day.
on the hour
at an exact hour, or on each hour, of the day or night:news bulletins on the hour
within the hour
after less than an hour.
Middle English: from Anglo-Norman French ure, via Latin from Greek hōra 'season, hour'