Definition of hour
2
: the 24th part of a day : 60 minutes
3a
: the time of day reckoned in two 12-hour periods
b
hours plural
: the time reckoned in one 24-hour period from midnight to midnight using a 4-digit number of which the first two digits indicate the hour and the last two digits indicate the minute
in the military 4:30 p.m. is called 1630 hours
4a
: a customary or particular time
lunch hour in our hour of need
also
: moment sense 1b
hero of the hour
b
hours plural
: time of going to bed
keeps late hours
also
: time of working
banker's hours
5
: an angular unit of right ascension equal to 15 degrees measured along the celestial equator
6
: the work done or distance traveled at normal rate in an hour
the city was two hours away
7a
: a class session
b
: credit hour, semester hour
after hours
: after the regular quitting or closing time
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Test Your Vocabulary
Who Knew?
-
- What is a ruelle?

Test your visual vocabulary with our 10-question challenge!
TAKE THE QUIZ
Anagram puzzles meet word search.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridged
Words at Play
Ask the Editors
Share hour
Time Traveler for hour
The first known use of hour was in the 13th century
See more words from the same century