year

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The period of time during which Earth completes a single revolution around the sun, consisting of 365 days, 5 hours, 49 minutes, and 12 seconds of mean solar time. In the Gregorian calendar the year begins on January 1 and ends on December 31 and is divided into 12 months, 52 weeks, and 365 or 366 days.
• noun A period approximately equal to a year in other calendars.
• noun A period of approximately the duration of a calendar year.
• noun A sidereal year.
• noun A solar year.
• noun A period equal to the calendar year but beginning on a different date.
• noun A specific period of time, usually shorter than 12 months, devoted to a special activity.
• noun Age, especially old age.
• noun An indefinitely long period of time.

from The Century Dictionary.

• noun A full round of the seasons; the period of the earth's revolution round the sun; more accurately, the interval between one vernal equinox and the next, or one complete mean apparent circuit of the ecliptic by the sun, or mean motion through 360° of longitude.
• noun The time in which any planet completes a revolution round the sun: as, the year of Jupiter or of Saturn.
• noun A space of about 365 days, used in the civil or religious reckoning of time; especially, the usual period of 365 or 366 days, divided into twelve calendar months, now reckoned as beginning with the 1st of January and ending with the 31st of December: as, the year 1891 (see legal year, below); also, a period of approximately the same length in other calendars. Compare calendar.
• noun A space of twelve calendar months without regard to the point from which they are reckoned: as, he sailed on June 1st, and was absent just one year.
• noun plural Period of life; age: as, he is very vigorous for his years: often used specifically to note old age. See in years, below.
• noun The older plural year still remains in popular language: as, the horse is ten year old.
• noun Incorrectly, a year of the Julian calendar.
• noun part of the sovereign's prerogative in England, whereby he was entitled to the profits for a year and a day of the lands held by persons attainted of petty treason or felony, together with the right of wasting them, afterward restoring them to the lord of the fee. It was abolished by the Felony Act, 1870.

from the GNU version of the Collaborative International Dictionary of English.

• noun The time of the apparent revolution of the sun trough the ecliptic; the period occupied by the earth in making its revolution around the sun, called the astronomical year; also, a period more or less nearly agreeing with this, adopted by various nations as a measure of time, and called the civil year.
• noun The time in which any planet completes a revolution about the sun.
• noun Age, or old age.
• noun the time of the earth's revolution from perihelion to perihelion again, which is 365 days, 6 hours, 13 minutes, and 48 seconds.
• noun (Eccl.) a commemoration of a deceased person, as by a Mass, a year after his death. Cf. A month's mind, under Month.
• noun See Bissextile.
• noun See under Canicular.
• noun the year adopted by any nation for the computation of time.
• noun the period of 12 lunar months, or 354 days.
• noun each year of 365 days, as distinguished from leap year.
• noun the period of 13 lunar months, or 384 days.
• noun (Com.) the year by which accounts are reckoned, or the year between one annual time of settlement, or balancing of accounts, and another.
• noun See Platonic year, under Platonic.
• noun See under Gregorian, and Julian.
• noun See Leap year, in the Vocabulary.
• noun the period of 12 lunar synodical months, or 354 days, 8 hours, 48 minutes, 36 seconds.
• noun See under Lunisolar.
• noun See Anomalistic year, above.
• noun See under Platonic, and Sabbatical.
• noun the time in which the sun, departing from any fixed star, returns to the same. This is 365 days, 6 hours, 9 minutes, and 9.3 seconds.
• noun See under Tropical.
• noun (O. Eng. Law) a time to be allowed for an act or an event, in order that an entire year might be secured beyond all question.
• noun any year of the Christian era; Anno Domini; A. D. or a. d.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The time it takes the Earth to complete one revolution of the Sun (between 365.24 and 365.26 days depending on the point of reference).
• noun by extension The time it takes for any planetary body to make one revolution around another body.
• noun A period between set dates that mark a year, from January 1 to December 31 by the Gregorian calendar.
• noun A scheduled part of a calendar year spent in a specific activity.
• noun sciences A Julian year, exactly 365.25 days, represented by "a".