[1] : 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.
      1913 webster

   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?
      1913 webster

   3. fixed or appointed time; conjuncture; a particular time or
      occasion; as, the hour of greatest peril; the man for the
      hour.
      1913 webster

            woman, . . . mine hour is not yet come. --john ii.
                                                  4.
      1913 webster

            this is your hour, and the power of darkness. --luke
                                                  xxii. 53.
      1913 webster

   4. pl. r. c. ch. certain prayers to be repeated at stated
      times of the day, as matins and vespers.
      1913 webster

   5. a measure of distance traveled.
      1913 webster

            vilvoorden, three hours from brussels. --j. p.
                                                  peters.
      1913 webster

   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 15deg, 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
see also:
year horologe horoscope after hours canonical hours canonical 
hour angle hour circle hour hand hour line hour plate 
sidereal hour solar hour the small hours to keep good hours 

[2] : WordNet (r) 2.0

sidereal hour
     n : 1/24 of a sidereal day

Sidereal >> S Words
Sidereal, definition of term: Sidereal
sidereal_pag1.html

Hour >> H Words
Hour, definition of term: Hour
hour_pag1.html

Sidereal Clock >> S Words
Sidereal Clock, definition of term: Sidereal Clock
sidereal+clock_pag1.html

Sidereal Time >> S Words
Sidereal Time, definition of term: Sidereal Time
sidereal+time_pag1.html

Zero Hour >> Z Words
Zero Hour, definition of term: Zero Hour
zero+hour_pag1.html

Man Hour >> M Words
Man Hour, definition of term: Man Hour
man+hour_pag1.html

Happy Hour >> H Words
Happy Hour, definition of term: Happy Hour
happy+hour_pag1.html

Kilowatt Hour >> K Words
Kilowatt Hour, definition of term: Kilowatt Hour
kilowatt+hour_pag1.html

Ampere Hour >> A Words
Ampere Hour, definition of term: Ampere Hour
ampere+hour_pag1.html