the interval between two successive passages of the vernal equinox over the meridian, being about four minutes shorter than a mean solar day.
See day (sense 5)
- Sidereal hour
noun 1. a 24th part of a sidereal day
noun, Astronomy. 1. the angle, measured westward through 360°, between the hour circle passing through the vernal equinox and the hour circle of a celestial body.
noun, Astronomy. 1. See under month (def 5). noun 1. Also called calendar month. any of the twelve parts, as January or February, into which the calendar year is divided. 2. the time from any day of one calendar month to the corresponding day of the next. 3. a period of four weeks or 30 […]
- Sidereal period
noun 1. (astronomy) the period of revolution of a body about another with respect to one or more distant stars