The Collaborative International Dictionary of English v.0.48:

Hour \Hour\, n. [OE. hour, our, hore, ure, OF. hore, ore, ure,
   F. heure, L. hora, fr. Gr. ?, orig., a definite space of
   time, fixed by natural laws; hence, a season, the time of the
   day, an hour. See Year, and cf. Horologe, Horoscope.]
   1. The twenty-fourth part of a day; sixty minutes.
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   2. The time of the day, as expressed in hours and minutes,
      and indicated by a timepiece; as, what is the hour? At
      what hour shall we meet?
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   3. Fixed or appointed time; conjuncture; a particular time or
      occasion; as, the hour of greatest peril; the man for the
      hour.
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            Woman, . . . mine hour is not yet come. --John ii.
                                                  4.
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            This is your hour, and the power of darkness. --Luke
                                                  xxii. 53.
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   4. pl. (R. C. Ch.) Certain prayers to be repeated at stated
      times of the day, as matins and vespers.
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   5. A measure of distance traveled.
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            Vilvoorden, three hours from Brussels. --J. P.
                                                  Peters.
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   After hours, after the time appointed for one's regular
      labor.

   Canonical hours. See under Canonical.

   Hour angle (Astron.), the angle between the hour circle
      passing through a given body, and the meridian of a place.


   Hour circle. (Astron.)
      (a) Any circle of the sphere passing through the two poles
          of the equator; esp., one of the circles drawn on an
          artificial globe through the poles, and dividing the
          equator into spaces of 15[deg], or one hour, each.
      (b) A circle upon an equatorial telescope lying parallel
          to the plane of the earth's equator, and graduated in
          hours and subdivisions of hours of right ascension.
      (c) A small brass circle attached to the north pole of an
          artificial globe, and divided into twenty-four parts
          or hours. It is used to mark differences of time in
          working problems on the globe.

   Hour hand, the hand or index which shows the hour on a
      timepiece.

   Hour line.
      (a) (Astron.) A line indicating the hour.
      (b) (Dialing) A line on which the shadow falls at a given
          hour; the intersection of an hour circle which the
          face of the dial.

   Hour plate, the plate of a timepiece on which the hours are
      marked; the dial. --Locke.

   Sidereal hour, the twenty-fourth part of a sidereal day.

   Solar hour, the twenty-fourth part of a solar day.

   The small hours, the early hours of the morning, as one
      o'clock, two o'clock, etc.

   To keep good hours, to be regular in going to bed early.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hour
    n 1: a period of time equal to 1/24th of a day; "the job will
         take more than an hour" [syn: hour, hr, 60 minutes]
    2: clock time; "the hour is getting late" [syn: hour, time of
       day]
    3: a special and memorable period; "it was their finest hour"
    4: distance measured by the time taken to cover it; "we live an
       hour from the airport"; "its just 10 minutes away" [syn:
       hour, minute]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "hour":
   abundant year, academic year, annum, bell, bissextile year,
   calendar month, calendar year, century, common year, day, decade,
   decennary, decennium, defective year, fateful moment, fiscal year,
   fortnight, instant, interval, juncture, kairos, leap year,
   lunar month, lunar year, lunation, luster, lustrum, man-hour,
   microsecond, millennium, millisecond, minute, moment,
   moment of truth, month, moon, period, point, pregnant moment,
   psychological moment, quarter, quinquennium, regular year, season,
   second, semester, session, sidereal year, solar year, space, span,
   spell, stage, stretch, sun, term, the time, time, time lag,
   time of day, time signal, trimester, twelvemonth, week, weekday,
   while, year



Easton's 1897 Bible Dictionary:

Hour
   First found in Dan. 3:6; 4:19, 33;5:5. It is the rendering of
   the Chaldee shaah, meaning a "moment," a "look." It is used in
   the New Testament frequently to denote some determinate season
   (Matt. 8:13; Luke 12:39).

     With the ancient Hebrews the divisions of the day were
   "morning, evening, and noon-day" (Ps. 55:17, etc.). The Greeks,
   following the Babylonians, divided the day into twelve hours.
   The Jews, during the Captivity, learned also from the
   Babylonians this method of dividing time. When Judea became
   subject to the Romans, the Jews adopted the Roman mode of
   reckoning time. The night was divided into four watches (Luke
   12:38; Matt. 14:25; 13:25). Frequent allusion is also made to
   hours (Matt. 25:13; 26:40, etc.). (See DAY.)

     An hour was the twelfth part of the day, reckoning from
   sunrise to sunset, and consequently it perpetually varied in
   length.


Bouvier's Law Dictionary, Revised 6th Ed (1856):

HOUR measure of time. The space of sixty minutes, or the twenty-fourth part
of a natural day. Vide Date; Fraction; and Co. Litt. 135; 3 Chit. Pr. 110.